The main problem with a TM rush is that the Treasure Maps actively antisynergize - each time you activate a pair you make the next pair much harder to connect. You could do this sort of thing with two or three or four TM’s for an okay BM strategy on a board with just nothing else going on, but you’ll have trouble on a lot of real boards with better Plan targets.
Realistically, you only care about connect once or twice, then you can trash the rest as you draw them. The point is that it makes getting the first activation extremely fast, and gives good odds on a second activation as well. 8 Golds straight into buying Provinces can end the game very fast, especially when Plan has thinned the Coppers and Estates from your deck.
What’s a best case?
T1 Plan
T2 Treasure Map (remember, only 5/12 odds you can even do this)
(Shuffle)
T3 TM
T4 TM
(Shuffle)
T5 Collide, Buy Silver I guess
T6 Province???
(Shuffle)
You now have a 13 card deck with 4 Golds, 1 TM, 1 Province, 7 Copper. Basically if you miss Province you, Buy one more treasure map and hope for a T9 or T10 collision? Let’s say you get one more Province one more Tmap, and T9 you get the collision, which is super low odds. Then you can potentially get Province 5 at T12-13.
That’s... comparable to the average case for Gear BM, for the absolute best case here. Leaves a bit to be desired?