I don't think it'll cheapen it, but I do know what you mean. It'll make it look more garish if they completely theme everything to match the lot.
I agree that it looks very nice now, but I would add a bit more themeing still. Especially the Mummy. Very hodgepodge. You have the entrance arch, then plain nothing. Then the new hanging artifact and box, then nothing. Then that Mummy statue, then nothing until you get inside the building. Idk, it always felt unfinished. With Jurassic Park you're a least completely surrounded by the foliage, etc.
That's why I think embracing the lower lot's real theme (being on the backlot essentially) would be great. I think making it feel MORE like it's in the middle of the backlot and the rides are active productions would be cool. It's a theme park afterall. Gotta have a return to at least part of the movie magic, like the film maker characters in the 80s and 90s, etc.
That's why I think adding some film props, filming rigs and film maker characters maybe would be fun. The props and rigs would be nice photo oops as well, like a camera/director rig, etc. Just a little bit of Placemaking. Because unlike in Florida, it works here in Hollywood.
But I would still update the facades on the lower lot a bit more.
Only thing is I'm not sure if the guests will embrace or understand the stark difference between the lavish and cohesive themeing of the Upper Lot (Wizarding World, Springfield, Despicable Me, etc), with the plain soundstage look of the lower lot. Would they understand that it's "in the backlot"? It worked before, because the entire park was plainly themed and hodgepodge. But what about now? I think additional themeing wouldn't hurt the lower lot.