On the note of sacrifice room items, I think I just found a bug of some sort here.
Trying out the Flame mech, right, with your revisions (which arent where the bug is), with it's usual 6 HP, I go into a sacrifice room, buy an item that costs 5, and.... instant death. I have no idea why. Has anyone else seen this sort of thing happen? Just to make sure it wasnt that specific item doing it (It was the mapping thing I bought the first time), I started a new run, went into the next sacrifice room, bought a different 5-cost item, and... instant death.
So that happened. Needless to say I was at full HP when buying, both times.
Anyway though, on the Flame Mech itself, it does have a much better feel to it now. The whole thing just seems more balanced and generally less one-sided. So I approve of all of that.
As for the damn blade.... bah, yes, I'll come up with something later. It's not a big priority at this exact moment.