The alternative is to make them all the type "Copper" (instead of trinket) so all the Copper interactions still work. It's a strange rules retcon, but one that could work. Replacing all 7 would be fine in this case, although they should then all be very subtle (you don't want to be playing 5 actions on your first turn).
I'll take it upon myself to post a full list of 7, each benefitting a certain type of strategy. Rare Coin benefits TFB (I will nerf it from $7 to $3, to precisely correspond to the lost value from estates when playing with shelters), Toy Bridge benefits +buys (I won't give it a +buy), one will be (+2 actions, +$1) for engines and those interactions, etc. One will be the victory card if I can word it somehow (maybe "Differently named Copper cards" instead of "Trinkets").
Keep posting ideas though.