Good news and bad news: While I did make some more progress, I'm officially abandoning this run. I have my fingers crossed that someone else will tackle this beast.
Progress below:
Link to video
Halfway through Protect the Gallimimus
I took my own advice and made a new smv that starts at Protect the Gallimimus. I make it through half the mission, and honestly I'm stoked at how this turned out. I tried out a new idea, which is to have 1 character jump at a time while they are overlapping, and it adds a lot to the idle running moments. It's very time consuming to figure out these sequences, and is probably a lot easier to handle afterwards via hex editing. Another neat trick is to shoot indefinitely at running enemies. Since bullets impact so quickly at close range, the 5 bullet limit of rapid fire weapons is basically ignored. In addition, tranquilizer weapons knock the enemy backwards, so you can load pellets into moving enemies for quite a long time. Another thing, at one point I slow down to shoot a landmine. This doesn't actually cost any time because I can corner boost back to the right edge of the screen.
The remaining level designs not yet seen in my WIPs are pretty cool. Here's some quick screenshots of Blockade, High Ptera and Seek and Destroy to show you what I mean:
So yeah, if anyone wants to take this up, they can use the 4.5 levels I've worked on. Hex editing is very straightforward since the game has basically no RNG or lag to speak of. In fact, the game as a whole is very easy to optimize. The bigger challenge is varying weapon usage, particularly on human enemies.
These 2 are my favorites.