WIP on YouTube
This is the WIP posted above, encoded for scrimpeh. If I recall correctly I have some more progress, but that's on another PC which I don't have easy access to.
The TAS is cancelled so far, by the way, because of background music issues. (The run also was not very optimized and seems technically improvable.) PSXjin hasn't fixed the BGM issue yet, as far as I know.
[EDIT]
I found a real time speedrun of the PC version of the game, by MolotokCocktail. See the first part
here. It contains some interesting routes and ideas:
-Downtown District (06:46)
1. Complete the Radio Za-Za mission (one of the green Loonie missions)
2. Shoot down Zaibatsu until Yakuza respect is maxed out
3. Complete the Get Zitzaki mission (one of the green Yakuza missions).
4. By level 4 cop level attained during 2 and 3, steal a SWAT Van
5. Complete the SWAT Van Swipe mission (first red Yakuza mission, just requires you to deliver a SWAT Van, which the player already has)
6. Complete the Stop the Tank mission (second red Yakuza mission). By now, player has about $500000 and multiplier x5.
7. Steal a bus, and load it full with people. (Move the camera to manipulate civilians to appear on the bus stop)
8. Rig the bus with a car bomb, and park it onto the road, next to more cars and civilians.
9. Trigger the car bomb. Player gets Expeditious Execution bonus, gaining 5x$100000, so the money count reaches 1 million, enough to complete Downtown. The player reached this in 06:46 realtime.
However, this route is not possible on the PSX version, because there don't seem to be buses in the game. It's also slower to perform some of the strategies, because the PSX version is changed to have less people and cars appear, making getting a level 4 Wanted level and getting a SWAT Van to appear harder.
-Residential District (07:40)
1. Collect the four Multiplier+1's on the map. Multiplier turns to x5.
2. Get 7 of the 8 hidden Wang Cars.
3. Save and reload the game to refresh the Wang Cars and Multiplier+1's.
4. Collect the four Multiplier+1's on the map again. Multiplier turns to x9.
5. Get three of the refreshed Wang Cars to get Wang Car Bonus three times (3x$100000x9=$2700000).
6. Wreak havoc with the Wang Car Bonus Tank until you reach $3000000, which is enough to complete Residential.
EDIT EDIT: This isn't possible on the PSX version either. Ugh, PSX version sucks.
-Industrial District (27:23)
Just plain doin' missions here, which as you might guess takes much longer than the other two districts.