I have a few inputs on Lucas, if I may.
As for neutral stages, myself and quite a few other Lucas mains hate Yoshi's Island. The stage messes with a lot of things Lucas can do. But FD is another stage that Lucas doesn't particularly shine on.
Lucases do like Battlefield and Smashville, so you guys were spot on there.
As for counterpick stages, I don't really have much experience on Castle Siege, but I wouldn't think it to be TOO bad for Lucas. Saying he's easily gimpable isn't the most accurate sentence ever, because Lucas does have quite a few tricks to get back to the stage, and Lucas only really relies on PK Thunder when he HAS to. For counterpick stages, I always ban Yoshi's Island for reasons stated above. ROB would probably do quite well on Frigate, as on the first transformation, Lucas can't rely on his tether on the right side, and would be forced to use alternative ways to recover, including PK thunder, which you can capitalize on. Japes would also probably be good against Lucas
As for Lucas' counterpicks, I've seen varied things. Where it's legal, Corneria would be a stage to watch out for, as Lucas can recover A LOT on the main gun/Arwing. I always try to counterpick this stage (sans where it's not legal). As for a universal counterpick, I have seen many Lucas players going to Brinstar (got this stage picked against my ROB against another Lucas and he did rather well). Lucas seems to do quite well there, even though ROB does fairly well there, too.
Hope you guys think this is some good input, just trying to help out where I can!