Hey there, I'm currently playing with the idea of making a 3D Seiken Densetsu(-styled Fan) Game. It will probably be top-down with a maximum of 3 characters.

The idea is to "fuse" Secret of Mana and Seiken Densetu 3. You have only three characters, but you can choose which character you start with (And having a different Story arc for each with different Endings/Bosses).

I dunno how I should design the battle system though. I want to have the ability to play in multiplayer over network. Having a start-stop system like Seiken Densetsu 3 seems to be too annoying. But I want to keep the casting of Spells in SD3 (More Powerful spells need longer to cast).

The Battlesystem will be more like Secret of Mana, while having to recharge to 100%, The Amount of Time to recharge depends on your Agility-Stat. (Higher Agi -> Faster attack frequency)

I also want to bring the class changes back, but also want to have a free choice of weapons. Do you have an idea how I should implement Special Attacks alá SD3, but keep a free choice of weapon, that works with classchanges? Because special Attacks alá Secret of Mana were too slow when charging the attacks.

It'd be nice if you guys could give some feedback for this idea.

Well, your idea is a bit crude to be honest.

The first thing that you don't really seems to be 100% sure how you want to handle special attacks. Yes, the special attacks on SoM are incredibly slow, specially when you want to use a high level attack (charge to 100% 8 times? really?), so I would say that the the SD3 approach is much better, I would go with that.

I also think you could add some gameplay to the special gauge, for instance some character could gain a bonus gauge when it hits a critical hit, one of the saber spells could add bonus gauge and, finally, a tanky char could earn points by getting hit.

As for spells, I don't really know how to handle it. When I played I had two problems, MP is boring and spells are either too powerful or too weak. In a quick brainstorm the only idea I could come with was that stronger spells (such as saint beam) should require gauge to consume, while weaker ones could be spamed.

Finally, a free for all weapon choices is great on paper, but it is far too much work and very small reward. Specially because in the end, one weapon will be better than others and people will simply ignore all the work you put on the other weapons. If you really want, focus two or three play styles per class. You could take a look on Soma bringer, they handled it quite well IMO.