I also thought about mesh related particles, but I think its hard to do something like this without a bone based model format.
If you want to use the g3d format for this, you maybe can do it with some of the ideas given here.
You have named meshes which you can probabaly can refer too. So you can use a fake mesh with only two vertices in it. You'll need 2 vertices, because you also need a direction for the particle effect. So one vertice is not enough.
All this looks a bit complicated to me. Maybe its better to support another model format one day ( ogre or whatever )
Thinking about particles in general some more realistic ideas for the moment:- Individual "burning" particle systems for every unit which indicate a damage ( an improved version of the "burnable" switch in the xmls ) .
- other particle emitter types not only "flames" for example:
flashes
electric shocks
something that rortates around the unit
....
I think there are endless possibilities!
Improved shots:
Currently only one particle system are used for a shot. But it would be cool to have more of them ( one is a "bullet" the rest is some eyecandy
).
new trajectory types for the shots
smoke behind the projectiles ( maybe this can be done with several particle systems for one shot )
and so on.
And another, not particle related idea:
Animated objects in the tileset! By this you can have trees moving in the wind.
(Maybe animated models in shots too
)