Keep it as is. You're still going to use up resources eventually. And there's already the risks run with Elytra already, such as falling from the sky, crashing into places, getting stuck in leaves and fences, etc.
As for jumping over walls, there have been ways to do it already without the fireworks, like pearling over or making some crazy launcher to move you up with slime blocks. This change I don't see impacting PvP, since you will still need to swap to a chest plate once you land, and swap out some stuff.
There's also the whole losing durability, so eventually you will have to land, whenever that may be.
People have done sky raids before on the server. All this change would do is encourage defenders to actually fight if things go over their walls. Or you can do the foolproof solution, and hide behind a door.
The way I see it, worrying about somebody flying into your base is pointless. Hide indoors, or fight. I'm going to stop before I go into a whole rant that's been preached before on here.
As a guy with a 5 block high faction wall and no PvP activity to speak of, I'm perfectly fine with the fireworks elytra in place. It's fun and would allow people to explore the maps, both of which I think are more important that worrying about raiders knocking on your rooftops.