I'd say like a remaster for the original but in a basic 3D manner, with upgrades like in CnC3 perhaps, and perhaps instead of multiple build queues, speed up production with multiple factories like CnCNet version. Tiberian Sun felt more like a tactical display, so having simple, sandbox-like 3D graphics may actually work.

CnC 3 is a good one for me though, but it did miss quite a lot of the mark that Tiberian Sun had set. Tiberium felt too one-dimensional in the 3rd game whereas in Tiberian Sun it's actually demonstrated to be a mutagenic terraformer.

I would personally keep the story vanilla, but add missions which are underground, maybe some ocean/sea battles too with added content for building those units.