OIS - cool concept, needs rebalancing.
Regeneration - I don't even know if you're referring to Pseudoroids or BME, but either way, you're nuts.
EX Skills - WOULD have been decent except for two things:
1. Find some ORIGINAL saber skills
2. Never, ever tie them to rank again. In fact never, ever think about ranks again. ZX is much better for having dropped them.
OIS was a decent system.
At first, it was hard for an old MMX mind like myself to get used to. Then when I saw it was the only way to do substantial elemental damage and that it beefed attacks, I didn't mind as much.
That said, yes, it is open to abuses. OIS should never have existed, then just beefed up the attacks and abilities of the forms.
But,
This led to the ZXA's system.
Now, you had ONE energy bar for every form that would gradually refill.
On paper, the system should have erased the Combat abuses and allowed for more flexibility regarding puzzles.
Any substantial basic attack (including ZX's charged-attacks, for crying out loud) were tied to this STUPID bar.
In the meantime, you're faced with enemies that are largely unharmed by basic attacks, and the only way you could avoid damage was to have the correct elemental attack, boss form attack, or Homing Shot (IF it worked in time) ready.
How would you retool OIS or BME? Yeah, I've said "Go back to Weapons", but is there another fresh, new way that isn't bad?
Lemme think...
...
Well, a button-activated system is clearly abusable, though only for solitary attacks - charge attacks still cost. If OIS ended at a scene/door/fight change or end, that gives you absolutely no flexibility for your first play of the stage.
And recharging doesn't work in combat. X3 proved that, already. And having one bar for everything doesn't really make sense. At best, it merely redistributes overall usage; at worst, it leaves the design teams and players devoid of options.
There's a key element here that Inticreates, and possibly Capcom, seemed to have forgotten, and it took Megaman 9 to remind them:
DO NOT TIE NON-BONUS PUZZLES TO ENERGYNow, they did still do it. Various destructible blocks via Laser Trident and the Tornado Lifts in the Wily Stages did just that. But, they left you plenty of Weapon Energy, UNTIL you got to Superhero Mode.
If you want that extra E-Tank, great, work for it. Then you've earned the ability to use it. If you're wanting to beat "Hard Mode", you can't have them, you need to prove your mastery (taking into account the human condition and reasonable control error; I'm looking at you, last room of Galaxy Man Superhero Mode).
Life is tied to how much you take damage; weapons prevent taking damage and improve combat performance, including clearing groups of enemies. Including execution, that's a matter of skill, time limit on how long your energies last based on how well you do.
So I think the best thing to do is to leave non-bonus puzzles solely to basic attacks and movements that cost nothing. Puzzles are a matter of knowledge, typically no time limit. Even if there is a time limit, once you learn how to do the puzzle, there's no stopping you from doing it again (see: Endless Mode, MM9).
The Normal Mode acquaints you with the terms of the logic and the game. There can be skill in the execution of the puzzle, but this should be left to Hard Modes. Say you passed Blazin Flizard's lava lifts the first time; you might not have completely fulfilled Childre Inarabitta's main quest objective the first time. It's almost impossible to have known how many switches there were, and where they were, what you were supposed to press, how you were to press them, and do it all while surviving long enough to see the end.
You could leave puzzle execution in Normal Mode, and indeed, only those who can think fast enough would pass the first time. In doing so, though, you stand to lose a great deal of the "fun" and replay value of a game,
not to mention customer base of people who play video games in order to get away from taxing situations that they deal with in real life that actually have meaning on the course of our world.
As far as EX Skills go, though, I agree. They basically are weapons, just without energy bars (and either weak or useless so it's not like having unlimited Jewel Satellite or Chameleon Sting).
Personally, I was hoping that EX Skills and the Pseudoroids of ZXA would have element/attack pattern combinations that were CLEARLY the weakness of another boss. Never happened.
-Fire/Ice/Lightning was good in the Zero serie, but it really was unnecessary to include it once again in the ZX
serie in my opinion. The same goes for the Pseudoroids. How about a poison/space/shield/ground/whatever based
Pseudoroid/weapon for once? To be honest, I am getting a bit sick with the many ice and fire bosses lately.
-Have Master Thomas reset the world in an highly enjoyable fashion. I am not really sure if he should be the main villain,
but if there is room for a new one once again, then definitely give us a new one once again! I applaud Inti's
decision of a different final boss in their Mega Man games so far. That does not mean that Thomas cannot be
a final boss, but right now, I am more interested into a new one.
On the fire/ice bosses, THIS THIS THIS. Take out the Fire/Ice/Lightning system, already!
On the final boss, how about this:
~Master Thomas resets the world
~Master Thomas is consumed/destroyed/is used as a vessel in the revival of Dr. Weil
~In a parallel fashion, Megaman X, Axl, Zero, etc. are revived and carry out the remainder of the game/final battle themselves.
All in some way that provides closure for any unpopular characters, and possible future loopholes for reviving ones people liked.