IOA could use more new rides... but USF also needs new non-screen based rides. Almost everything scheduled for USF has heavy screen usage, in a park already full of heavy screen usage. SLOP would help very much.
I'd say, either have SLOP replace Shrek and make the opening area "Illumination Boulevard", OR build SLOP in the Toon Lagoon amphitheater spot, as well as a moved Minion Mayhem, Super Silly Fun Land, and a Minions Movie dark ride all in the Dudley spot. Popeye and the Olive can stay, as that IP is still relatively well known (and may even be getting a reboot soon) and Popeye is a great ride all round. Then, both the Shrek 4D and original Minion Mayhem buildings are demolished, and a proper entrance plaza to USF can be made.
The first option seems much easier and helps with the screen problem in USF, but makes the entrance area even more congested. The second one seems much harder, but helps fix Toon Lagoon, the screen problem in IOA (which isn't as bad as USF, but is getting there with FJ/Kong/Spidey), and the entrance problem in USF, and slightly helps the screen problem in USF, although by removal, not addition.