
If it works similar to the Geomod technology in Red Faction, then it should only be able to affect pre-determined areas of the terrain. In that case, then it shouldn't be a problem with gameplay, since the mapper could choose what terrain he wanted to make alterable. As for temporary, I don't think it would need to be, but there could be a limit on how many alterations the terrain can have. When that limit is reached, terrain can no longer be altered.
If it was implemented this way, I don't see any problems with it, and it could in fact be quite entertaining. Perhaps the gravity vortex could pull on the terrain slightly, so if a vortex went off over a flat section of land, there would be a shallow hill afterward? Would really accentuate the true power of the vortex... And redeemers could make craters...
Wow that could be fun. Blow a crater in the ground then hide in it and ambush some poor sod that says "ooh look at the big smoking crater!" and blunders in...
A wallmaker device would be perfect for CTF...
And if there's a limit to the number of alterations, perhaps there could be a terrain restoring tool that removes any alterations it hits, returning that part of the map to its original form. Then, new alterations could be made elsewhere. For instance, in a CTF game, an "engineer" type player could have one of these and go around repairing damage to the base or removing enemy walls, and use something like a detpack to blow new holes in the enemy base...
It would add a whole new dimension of strategy to the game, and be an excellent basis for building a class-based CTF. Imagine that, class-based Chaos the Flag with constructable/destructable terrain... *drool*