Personally, I like Legions to be more player dependent, than environment dependent. I played tribes(only for a short while though), and it really wasn't my type of game. Tribes was all about strategy, timing and team skill. To prepare for a match, a professional team would have to think on, how to place their deployables, like mines, reload stations etc, for hours and hours and train. That would be fun, yes, but not in Legions. For me, Legions is supposed to be a 'less complicated' game than Tribes, but faster. As you said, NYPD, Tribes was not about skiing, and skiing was actually a bug in the game. But, Legions is made for skiing. Get the difference? I come back from college, stressed out. I just wanna start up a game, pick a class, shoot some people and log off. I just wanna play a game, which requires more of my instinct, than my mind, and you can survive an evening game in a public server, in Legions, with just that. If I really want to put in my mind, I would, by sorting out effective cap routes in a map, judging the positions of my players, whether they need any changes, stuff like that. It is a completely different story for Tribes. You'd have to think, every time, to survive in a CTF game, and I hate it, when a game tries to force me to think, and not let me go ahead in the game(I found some RPG games to be like that, at some points).
When I said; Legions is more player dependent game, it is. Everything in the game, needs to be done, personally by the player himself, not with the help of any detachable machinery or vehicles. If you want more defense, you'll be switching players, not upgrading to a mother ship(sorry, don't really know the names of those things in Tribes). It's a small and simple game, where player positions and speed matters and nothing should effect that. If Legions really need any expanding, it should be in the form of classes, so the player can have more versatile options, while choosing. Other upgrades can be weapons, maps and whatever the developers can think off, and it'll all be done without harming the speed of the game-play. If you really want Tribes, wait till January, 2011, and you'll have your game; Tribes Universe.