I'm nearly out of space with my Omega stage slots so I was wondering if there were any Melee stages that could be ported over without too many issues. So far I have Temple, Skyworld, Pyrosphere, Duck Hunt, Battlefield, Big Battlefield, Coliseum, The Great Cave Offensive, Town and City, and Smashville ported over for the normal Melee stages.
iirc, Kongo Jungle 64 and Mario Galaxy work for new stages, and support animated collisions.
In general, simple stages without any weird transitions or hazards should work. Stages like Yoshi's Island and Windy Hill zone have custom stages that go over them, but it would take a bit more work to put something new there.