Depends. Personally, I'd like it there was more to see here. I don't care about puzzles, so they can go fuck themselves. Just wish to see more of it. So making it bigger will do the job for me, adding in an area or two, showing how other UBs live and such. That would be improvement for me.>plot relevance
The last one ties into this. Now, not only is it bigger, but you spend more time here. Maybe get dragged before the final confrontation and have to make your way out of here, fighting through weaker UBs and returning as a Faller. And you can also expend upon the Lusamine confrontation here, having the battle be dragged on, as Lusamine's Pokemon stall you while she catches a new team of strong UBs with Ultra Balls, in then she fights you with UBs a second time around.
Still, there are many ways to go about it. That's just the first two things that came to my mind.