Here's something I've been working on for some time, I believe you'll see what I'm talking about:

Explanations of locations:
1. Here you may find a BF Injection, very good on offroad, unlike other cars.
2. An elevator to the rooftop of a building where you may find a chopper or jump to another building.
3. An elevator to the rooftop, you get a good sniping/long ranging view from here. Also many objects to take cover behind and ability to jump off to another building with a car/bike.
4. You may go to the top of the building with an elevator, big fighting space, many buildings to jump on around.
5. An alleyway, also many turns in which you can quickly turn without the cop noticing, this'll give you time to escape.
6. A part of an alleyway stated above, here you have the path to the big offices building and 2 turns.
7. A very good stairway, good for bikes and quick turning cars, path to the bridge that leads to Prawn.
8. Big building with many offices, the biggest stunting place known in game, very good for bikes such as pcj.
9. A ramp that will lead any faster cars to the roof of The Greasy Chopper bar. Good for long range shooting.
10. A big parking space. Many cars parked here, much cover, big space for fighting.
11. Here we have a shortcut, if done right it will give you time and make the follower of yours crash into a lamp post.
12. Many alleyways, good for on foot chasing, many places where you can quickly turn.
13. A shortcut that leads to Leaf Links, here you may go to the other side of the island faster. There are a couple of crashed cars there, they will make your follower crash into them.
14. A pay and spray, good for a quick repair, short way to No. 15.
15. A path a little lower then the ground level, good for precise drivers. Also 2 small paths from the two sides, you may easily fool the cops while running on foot here, big combat space.
16. Small alleyway near the bank, good for on foot chases.
17. An alleyway with stairway to the roof of a building, good for bikes and on foot chases, boxes blocking the ath for bigger cars such as police cruiser.
18. An alleyway, big combat space at the right side of it, good for on foot chases, box blocking the path for bigger cars.
19. Again an alleyway, same as two above, stairway to a rooftop.
20. Big combat space and a couple of ramps from which you can jump over the fences.
21. Same as No. 20.
22. A pay 'n' spray, good for quick repairs. There's a place nearby from which you can jump to a big roof (can be done with pcj only, not accessable to any cars).
23. A shortcut that leads to one road to another, good for quick turning and drifting, fools cops oftenly.
24. Here you may find a place from which you can quickly jump from a side to another over the water and grab a boat.
25. The 8 ball's shop, giant fighting space and a couple of shortcuts that lead to ex IT HQ which contains a dinghy and a reefer.
26. A chopper and many boxes and other objects for good cover.
27. An airport road from which u can jump to the higher one (may be done with pcj only).
28. A place from which you can jump to the roof of the Escobar International building, can be done with any kind of cars.
29. An army base, a couple of big vehicles, watching towers, practice range, all good for on foor fighting and chases.
30. A place which contains a squalo, from here you can also jump to the other side which has a Cortez's yacht in it. The jump can be done with fast cars only.
31. A small opening that you go through with a bike, oftenly makes cops crash in it with cars.
32. Big fighting space and quick access to the main road of Starfish, good for on foot chasing.
33. A place that leads to an alleyway with many places to turn, good for on foot chases, also contains a squalo.
34. A place that leads to a big mansion with a pool, many ways to escape to the other side and you can also fool the cop so his car falls into the pool. Once it does, you can't retrive it.
35. A place accessable with bikes only, the path that's guarded by a fence, unreachable by cars or bullets.
36. A wriggly road that leads to the main road, very good for bikes.
37. A big alleyway, many ways to escape and hide behind the houses, good for bikes and on foot chases.
38. A place that leads to the apartment 3c, good for suprise attacking.
39. A palm in front of Pole Position club that oftenly makes the follower crash into it, right around the turn.
40. A big parking with many floors, good for cover fighting, sniping and on foot chases.
41. A path that leads to a big alleyway with many turns around, great for bikes.
42. A shortcut that may lead you to the main road or the parking, good for losing visual of the follower.
43,44, 45,46,47,48,49. (down, Ocean beach and Washington beach) Many alleys, good for bikes and on foot chases.
50. A good shortcut from wich you can jump to VCPD or go to Starfish.
51. The building site, many ways to escape while on foot and on bike, you may jump to Spand Express from the 1st floor.
52. A shortcut that may lead you to Malibu club, good for gaining time and hiding.
53. A ramp that you may jump over the sea from.
54. A shortcut that oftenly makes the follower crash into a big palm tree.
55. A roundabout good for gaining time.
56. A path that leads to the beach, good for on foot chases.
57. A shortcut leading to Vice Point, also there's a palm you can climb on and jump on Malibu roof from.
58, 59, 40, 41. (40 and 41 up, vice point) Alleyways good for bikes and on foot chases, big fighting space, a few roofs accessable.
42. (up) A shortcut with a couple of mailboxes around, good for bikes and making the follower crash.
43. (up) An alleyway with stairs that you may jump to Prawn from.
44. (up) A big parking with many cars around, a ramp on the top that you can jump on road from.
45. (up) Big stairways that lead you to the rooftops of a couple of buildings, good for on foor chases and bikes.
46. (up) A big fountain that you may jump from to a roof of any nearby building with a pcj.
47. (up) Film studio, many places to take cover at, big fighting space.
I've been working a lot on this, I hope it'll help some people.
Credits to Rapture for adding my name on the top right screen.