Ooooooooookay. I havent been awake very long, so forgive me if this doesnt make much sense. Logged in, had a look at the forums here, saw the other thread with the funky purification idea.
I'll go into a few things here.
First of all, the merc coins themselves. They werent a bad idea.... they gave the player something to collect, which is never a bad thing in a platformer. Items in a game like that dont always have to be awesome powerups or stuff like that, even very simple things that have minor effects can help. Look at normal coins in the Mario games; an individual coin does next to nothing, as you need a full 100 of them to have them do anything. But, in the earliest games particularly, this still WORKED.... these were something for the player to find and grab, which made things that much more engaging to them, added more "reward" to various areas without actually breaking anything, and further rewarded diligent players for picking up as many of them as possible and not missing too many.
The problem was what the merc coins DID. Right from the start, I didn't see how they could really be brought to work as the idea of an AI partner just sounded a bit iffy to start with. The idea that I had had was a little different. Like the purifying idea, I've had the thoughts of taking the merc coins, and having them be something that is used not on the platforming bits, but on the strategic map. Not for purifying though. My idea would be, to have the mercs be able to perform special tasks on the worldmap that you cannot do yourself. For example, if you REALLY wanted to re-build a special building for some reason, perhaps the way to do it would be to pay the mercs to do it. Or all sorts of other potential ideas. The merc coins could almost be the player's answer to Demonaica's spells.
The purifying idea, I would be somewhat against. It'd sorta be messing with something that I dont think is broken to begin with. I've posted my issues with the strategic game in that other thread, but those were all purely balance issues..... not "I think this mechanic needs changing" issues. And a mechanic like that *would* lead to grinding, which to me is never a good thing. The coins in general might lead to that, really. There would have to be some sort of thing in place where coins only appear in corrupted tiles, and you only KEEP them if you pop the wind generator.
As equipment goes, I really like the idea of it, and I think they work nicely with the enhanced duration. The problem with them, as I see it, is that some of them are kinda baffling. It can be tough to figure out what something is doing, and this points out a couple of problems to me. First, not being able to tell what something like a powerup is even doing is going to be frustrating to players. But secondly.... if I cant even tell what the thing is doing, then it cant be all that strong/useful. Meaning, basically, that while there are some nice effects in the equipment system, some of them are extraneous and could simply be removed, or enhanced to matter more. The negative ones.... I dont think added much to the game to start with. Not when you have the names visible before grabbing them. The "negative equipment" idea is one usually reserved for Roguelikes, and this is because you often CANT see even what an item is called until you do something or other with it. But there's also the idea of frustration here again.... this is a pretty hard game to begin with, and I think it'd just annoy players to reach an out of the way treasure box, only to have it make them move like a brick in sludge until they take a pile of hits.
So, a few things with that. First, as I said, take the more confusing effects and either change them, or make them stronger, so they matter. Second, tell the player just what the thing is doing. This knowledge is the sort of thing that would actually be factoring into how they decide to approach each combat situation, and it would add even more strategy to this.... but not if they cant tell what it's doing! Third, remove the negative ones. They just dont add anything to it. Fourth, definitely give indicators on the screen of how much longer the thing is going to last. I've so far found myself occaisionally pausing the game just to check that number, when I had something useful on. Fifth, dont change the "one at a time" rule, as I think that's an important one, and leads to more of the important decision-making kind of idea. Dont change the bit where treasure chests tend to appear in groups, either. Again, having the player actively make a choice when they appear, not a bad thing. If you can do these things, and keep the effects varied and interesting, I think this would add alot to the platforming. The equipment doesnt need to last huge amounts of time.... they ARE essentially powerups. And in their current implementation, they'd work nicely with the "concentration" idea, in that the player is rewarded for not crashing into enemy bullets and such.
I would also be against the idea of having piles of these that you use from the world map. Sorta interferes with other mechanics that are already in place. From the world map, you already choose your spell set to use.... but there's also the perks, as well, and plenty of incentive already to collect those (and it's also a mechanic that also just works very well already), so that you have that many more options and such that you can choose to take into a given area. Dont downplay these by adding another version of that idea.... keep the equipment strictly one at at a time, and done entirely in the platforming bits.