Having any score that is not related to time may be complicated on a speedrunning website. This is why I only submitted ILs that are completed faster or slower depending on your performance. Your idea sounds nice though. You could create the topic GTA SA record book volume 3 on gta forums. The volume 2 is quite outdated.

I recently submitted run for Driving School (complete), all 3 couriers (LS, SF and LV), Valet, Yay Courier and BS Cash. The later 3, even though not missions, have at least 2 of some elements that make them similar to missions like: pass/fail conditions, change $OnMission when started or passed/failed, increase missions attempts and missions passed stats. I think most will agree the first 5 submissions should have their own leaderboard, but what you guys think of the later 2 suggestions (Yay Courier and BS Cash?