I don't see this combo work, even in a Province game. I don't know how much turns it takes for Masterpiece to get to 4 Provinces, but I think it will be faster (a little less resistant to greening, but still pretty good in that aspect). And that is bad for a two card combo!
Suppose we manage to connect two treasure maps without any support on turn 7, and on turn 8 we do the big masterpiece buy. Then indeed we have a deck of 4 Gold, 13 Silver, 7 Copper, 3 Estate and 1 Masterpiece (and 1 remaining TM), but one think the OP forgets is the following. All our Golds and at least 10 of our Silvers are in the discard pile. In our deck, we have 10 cards remaining consisting of only Coppers, Estates, and 0~3 Silvers. This means we still have crappy hands turn 9 and 10 (which together has 1 Duchy buy, if we are lucky), and the real greening can start only on turn 11. And then our average buying power is about $8 per 5 cards, which means we have just over 50% chance to buy a Province on a given turn. This means it will take 16~17 turns to reach 4 Provinces. Pure Big Money does just a little worse than that. And this is only under the assumption that your Treasure Maps collide turn 7 without any support.