1. 4 wheel drive sand king or the ability to lift some of the 4x4 trucks.
2. Ability to save a mountain bike in the truck bed so you don't have to steal the bike and bunny hop it in if you want to drive up and bike down a mountain or something. Or you could link them like the fog light bars in a truck bed currently. What I mean by that is the fact that the fog light bar thing can break off but once the vehicle is repaired it returns. Make it the same for the bike. Once the bike leaves the truck it is gone until the truck is repaired or a more stream lined albeit unrealistic way to reload the bike into the bed. Would have to make it so the bike isn't it's own individual personal vehicle though if you went the repair route. Maybe make it so only the owner of the truck can ride the bike and it becomes useless once you repair (dupe) it. If any of that makes any sense.
Maybe add a way to select a bike/motorcycle in the garage to add them to a truck bed. Limit it to only one vehicle you can load that is parked next to the bike rack or something. If this is a good suggestion it would be cool to save a trailer with a jetski or something in a similar fashion.
3. Add a custom quick waypoint. So you can set a location using a similar mechanic to the point of interest marker, but so you can select it via the quick waypoint menu and allow us to name it whatever we want. Probably limit this to one or two custom locations so it doesn't get messy.
4. Ability to get rid of or store certain wardrobe items. I hate the fact that I bought those stupid stank shades and now have to scroll through them every time even though I never wear them (just one example). Same suggestion for the masks/hats.
5. Ability to change the lighting in los santos customs so you can see what the paint job will look like in the sun/night/fog/rain or whatever.