You could use bigger bricks. The constant use of 1x1s and 1x1x5s kills it.
1x1x5 was the main block used, 1x1s was only used because when I built the entire thing, I used macros where the entire thing was pre-built, meaning there was a double 36x36 between floors, and because I added the training rooms non-macro, it was easier to use 1x1s in the macro (one column, not the entire thing pre-fab) instead of measuring out 1x1x5s and and 1x1f to fill in the gaps.
Anyway, I know it is kind of spammy, and I might come back through on some of the floors I haven't furnitured and make the walls out of bigger bricks, It's just when I was building it, I've run into some problems before using bigger bricks, and It was just easier to use 1x1x5s, I really didn't foresee the problem of massive lag.
And once you get inside, it's not that bad.