Well I've been playing this game and I am going to try to play more before I judge it too much but there's something that's bugging me about it and I was wondering if anyone could answer this question I have...

In order to get A or S rank (so you can get the EX skill from the boss) can you truly not use any Elves at all?  It just seems kind of counterproductive that you go through all the work of finding the discs and then in order to get a high rank you can’t even use the abilities from the Elves at all.  Hopefully there is a way to circumvent this issue.  But I also noticed when you beat a stage with A rank you can’t even go back….so basically it seems like you can never use your Elves if you want EX skills.  I just find it frustrating that they don’t let you return to stages to try to increase your rank or replay them – that probably would have really improved this issue. 

Also, is there any way to expand your life energy (without using an Elf in the stage that lowers your rank)? 

Thanks.

The whole rank system is just for hardcore Japanese gamers who like perfection.  You'll notice that Zero 3 is an extremely easy game if you use all of the elves.  I also think there's some sort of New Game+ mode, but my memory is a little fuzzy on that.  Additionally, there are some elves that will give you an instant A rank, so if you're 100% sure you'll be able to beat a given boss, use them before hand to guarantee getting the EX skill.

The ranking system in the Zero games is an absolute bitch and mainly there for hardcore players. It's generally better to forget about it and just try to enjoy the ride. The fact that the EX skills system got tied into it is quite annoying, though.

That said, remember Satellite Elves - you can equip two at a time, and they won't decrease your mission rank ever. So for example, the elf Maltina can be used to double your life bar, and can be used as a Satellite Elf without lowering your mission score (after spending energy to convert her into a Sattelite Elf).*

Of course, you have to collect the damn things first...so, if you don't have great Zero skills, the best way to earn the EX attacks is on a second playthrough, since you can pick a clear save and restart the game with everything you acquired in that save.

*I think. This is based on what dim memories I have and interpretation of FAQs.