I've started going down the same path. I put a Baja light kit onto the gf's KLX140L. They have a lot of potential it seems. Guys in asia are up to 60 000 kms on them.
I'll have to get some risers for the green critter, too. Hopefully the cables are long enough. I hear the front of a KX100 is a bolt on for this bike.
I have not seen and larger tanks for them, yet. I have a 12l KTM tank on the shelf. I'll see if I can make it work somehow.