As someone who was at RAP for Victoria United and later Victoria HIghlanders (yes they played there a couple of years) I have spent lots of time thinking how best to improve the park.
To add to your good suggestions: build a stand over the sidewalk on Cook St. An arcade covering the sidewalk would allow the maximum seating area inside the stadium without losing any sidewalk.
At the corner of Cook and Caledonia, where a tiny, pointless parking space exists, build an outward-facing pub that includes an inward-facing patio to create a VIP club atmosphere for games. The facility could also be used for watching away games on TV and general providing ongoing revenue and helping to define the village that has developed in that part of Cook St.
yes that corner is quite sad.