Yeah, I see no reason why you couldn't take Lavaridge.
However, if we are going by the Akira-verse, here are some gyms I see available...
??Cinnabar?? (Have to ask Wily)
??Goldenrod?? (Have to ask Sky)
I'd say pretty much all of Hoenn is questionable or possibly up for grabs, with certain gyms depending on certain people
Same as above