I’ve only just discovered this topic and realise that almost 5 years later I may have missed the boat, however here is my

I have to break it down into smaller more easily digestible chunks for my tired old brain so…
Threat Tokens / EWP deckWhilst I don’t personally use an EW deck or Dungeon deck*, I’ve always enjoyed reading about the concept on this forum and am supportive that it could be a great addition however the key to success here I think is in making sure that the deck is varied but it still powerful enough to be relevant but not too over-powered that the entire outcome of the game is determined by which cards or combination of cards are drawn from the deck, an important and tricky balancing act.
*I have a golden house rule (link in my signature) around rolling “Snake Eyes”

on the movement dice triggers a WM to appear which is my way of
covering off the lack of time pressure in the game, so this fills that gap for me.
Linking Threat Tokens / EWP deck to player choicesAgain, I’m not opposed to this idea, but I think it makes the important and tricky issue of balance even more important and tricky than would be the case without this link. If players conclude that the deck is too strong (even if this isn’t actually the case but is only their perception) then they will just choose to drop the search option and take their chances with suffering hits from traps, equally if they decide it is too weak then they’ll just choose to “over-search” and the mechanism loses its value. As I said above balance is key, but this change makes the balance even more critical.
Search ChangesCombining Searching for Traps & Secret Doors together is a no-brainer for me because I still play the Classic edition where the two are already combined.
As for the rest of the proposed changes to the search for traps & secret doors aspect, they seem to be intended to resolve the following issues with the conventional rules:
1) Searching for Traps and Secret doors is dull/methodical/procedural/boring/unimaginative/flavourless
2) Mind points are under-utilised
3) Dwarf isn’t any better at finding traps than the other heroes even though his description indicates that he is
4) The Wizard to preserve Mind points and not engage in spellcasting additions that cost Mind Points
5) The Talisman of Lore is not relevant for the Barbarian
6) The heroes lack meaningful differentiation
7) Quests are too easy
8) There is a lack of penalty for time wasting on the heroes so they can dawdle without consequence
Whilst I agree wholeheartedly with points 1,2,3,6,7,8 being issues under the conventional rules I think that point 5 is just a continuation of point 2, any change that makes Mind points more utilised will make something that boosts them more significant.
Point 4 puzzles me a little as I’m not aware of any situations under the conventional rules where the Wizard chooses to expend Mind points to engage in spell casting (and even if he did then isn’t spellcasting what the Wizard is for, his primary function, otherwise the character would be named "The Searcher"?)
However I think the proposed rule changes have some issues
(A) By far the most common scenario in a room or passage is that it doesn’t contain any traps or secret doors, despite this being the most common scenario, this isn’t mentioned in the OP, but I presume the EWP would still need to roll dice behind the screen before telling heroes that they haven’t found anything. This feels like it may consume a significant amount of time in the game with little added value.
(B) Making the finding of secret doors conditional, even if the heroes do search for them in the right place, has the potential to lead to a significant amount of retracing of steps and re-searching to find an objective that is concealed behind a secret door (which is fairly common in the official quests). As mentioned an enterprising EWP could circumvention this issue by “forcing” the outcome of the hidden rolls but this places an expectation upon the EWP which may not be appropriate for some 10 year olds.
(C) Mind Points are a measure of a character's wisdom and a magical aptitude. They show how well they can use magic and, more importantly, how well they can resist it. The game text explicitly mentions that the Dwarf is the best at spotting traps (although the rules don’t reflect it) and I would imagine that the Elf with his acute senses and the Barbarian, raised in the wild Borderlands where being quick to spot and react to danger would have been essential to survival, would be close behind the Dwarf with the Wizard, whose life experience has been focussed around the realm of magic rather than the mechanical, would be the last on the list for spotting and disarming traps. This ranking of Dwarf followed by either Barbarian or Elf and in last place the Wizard for searching does NOT map to the MP attribute that places them in almost the opposite order so taking into account what Mind points are defined as being a measure of and the heroes “search” ranking not correlating to that attribute I’m puzzled as to why people insist on trying to force the two together. Agreed Mind points are under-utilised in the base game, so utilise them more (some ideas on how to do this are included in the links in my signature) but in ways that fit the attribute.
(D) By introducing searches that cover a smaller area, you significantly increase the number of search opportunities in the game from one per room/passage so roughly 20 in a typical quest to potentially 100s which has the potential to cause a number of new issues or at least exaggerate existing issues.
I get that the threat tokens are intended to discourage over-searching, but this change still opens up the possibility of players choosing to conduct 100s of searches in each quest that I think would make the game very dull, very long and potentially unplayable (at least in the sense that no one is likely to want to play it again)
An extension of point (A), the vast majority of individual squares on the board searched will not contain anything (I don’t mean that you won’t find anything, but that there is nothing to find) because most squares on the board don’t contain a trap or secret door. This creates a needle in a haystack situation (made worse by the fact that you can’t tell whether you found nothing because there was nothing to find or because you missed it, so do you double up on your 100s of searches?) combined with something of a paradox, in that players need to guess which squares may contain something and may be worth searching, based on…what? You can’t see a hidden trap or secret door, by definition, so are you expected to guess at what a quest creator was thinking when they designed the dungeon? Are we expecting the quest creator to second-guess this and so place things to find in the squares that players least expect to find things or place things in squares that are more obvious?
Essentially with this proposal we are hugely increasing the number of search opportunities in the game, and at the same time discouraging the players from taking too many of these opportunities, so we are expecting them to actually search a far smaller sub-set of the full number of search opportunities that before, whilst admitting that they don’t know and can’t be expected to know which ones of these vast range of search opportunities are actually likely to reveal anything.
I can see these rules working in a limited sense if and only if players happen to behave in a certain way, but a far likely outcome in my experience is that most of the time they won’t or can’t behave in the required fashion so the rules won’t work.
For me personally if you recognise and want to “fix” the issues in the game that are numbered at the start of this post then I would suggest that you consider some of the changes included in my Golden Rules which include better utilisation of Mind, making the game more challenging, scrapping search for traps and secret doors entirely, combining the spot & disarm trap rules and more.