I'd suggest the fully charged weapons have different properties instead of just more projectiles.
Only the last charge will be different, for example the Force Dash.
Some weapons such as a the following missiles are a bit over powered.
Missiles are quite weak and also follow explosive type projectiles, so they don't always go to enemies.
I can use that weapon and spam all day since it shoots 2 per shot, much more beneficial comparing to X-buster/phoenix buster.
All special weapons have energy meter unlike the buster that have a fast rechargeable meter. It is my intent for people to actually want to use X weapons unlike most players that just spam buster shots.