I always thought a "Legion Worlds" would be good for Adventure, maybe a few in depth comics about alien worlds of Legion people where things work very differently...
That would be so cool! I remember the Curt Swan/Jim Shooter issues with Mantis Morlo where we actually got to SEE the Legionnaires' respective homeworlds. Daxam was another "future world" with weird buildings and so forth, but the single most fascinating was Dream Girl's homeworld.
The idea of an entire civilization that has precognition is an entirely mindblowing idea, and I'm really glad Jim Shooter didn't wuss out on this frankly, courageous idea. He showed us what life was like on Nural - as car accidents are known in advance, papers are settled out of court. There is no gambling, and as election results are known in advance, nobody ever votes!
I also loved any Legion story set on Imsk, where EVERYBODY had the power to shrink - as in there were FUTURAMA style transport tubes that only the inhabitants could use by getting small as they were six inches tall. It was also rather trippy to imagine that Imsk ITSELF was shrinking!
Though the Mark Waid Legion reboot has been fine so far, one of my favorite moments was when Colossal Boy demanded his name be changed to "Micro Lad" because he was from a planet of giants, and his power was that he could shrink to six feet tall.
Also I'd like to see a modern, global force of non-powered adventurers that included the Sea Devils, the Challengers, Rip Hunter, Cave Carson and maybe even a peacetime Blackhawk team.
Wow, this would be a fantastic idea.
The thing about the Blackhawks and Sea Devils is, there's been something like three decades of progress in terms of vehicles and vehicle design - just crack open any issue of Popular Mechanics and you read innovations for VTOL (Vertical Takeoff and Landing), GPS systems and laser pathfinders, uranium tipped ammunition, and so on. If you give the book to a real techie-type who's crazy for engineering and machines, it might be a lot of fun.
I really, really enjoyed the Sean McLaughlin run on AQUAMAN back in 1989, and while it only lasted a few issues, it was fantastic to see the Sea Devils again.
And those jet skis of theirs...if I could have any comic book vehicle, give me one of those! (Or Thunderbird-3.)