FWIW, Dolphin does emulate disc read timing and seek timing - completely inaccurately, but there is a delay added when loading data from the emulated disc.
Has anyone actually tested changing this delay and checking if it has any effect on what you're talking about in MP? As far as I can remember, nobody reported any result related to this, so you're not even sure if that issue comes from disc delay or not.
If it does come from disc delay, then you need to figure out whether it comes from bad read speed emulation (doubtful - sequential read on a GC DVD is pretty fast, around ~10MB/s) or bad seek speed emulation. A good way to check that would be to trace all the DVD operations done during a MP room loading and computing the estimated time spent seeking vs. reading. Bonus points if you can patch IOS on a real Wii to give you the exact time spent in each DVD operation.
No developer is going to care about an issue if people spend years complaining loudly about it without at least trying to analyze and debug it.
Pierre "delroth" Bourdon <delroth>
Dolphin Emulator developer