I have one thing to say...

The player skeltons cannot be changed so Ewoks vrs Jawas is impossible pretty much.

Edit: Second thing to say actually....

If the devs were crazy about this though.... They could  make tiny "walkers" that were actually Jawas and Ewoks. Then set all spawn points for each team to be spawned into the vehicles and make them unable to exit. Multiple classes could be made with alternate spawns and the selection would be random unless the mapper made 2 or more spawn groups and labelled them on hte minimap

But guys... Its not going to happen.

"Munchkin: One who, on being told that this is a game about politics and intrigue in 17th century Italy, asks to play a ninja."
— Andrew Rilstone

Yeah they can, but I don't think on a map per map basis.
I'll try and find the BF Editor screenies of short men (kinda like hobbits).

Edit > Found it - http://bfeditor.org/forums/index.php?showtopic=8559