First of all, I seriously hope they bring back the GTA IV car handling. But I know that's never going to happen. Perhaps modders might be able to do that.
For graphics settings, here is what I want:
please make it scalable with more CPUs
avoid using the CPU to do compute tasks like physics and other things, use the GPU for that
a wide variety of screen resolutions to choose from
different graphics APIs: DX9, 10 or 11
a v-sync toggle
an option to change the quality of textures
texture filtering options where the lowest should be bilinear and the highest should be 16x anisotropic filtering
a plethora of anti-aliasing algorithms including: FXAA, MSAA, SMAA, TXAA (probably not going to happen) and SSAA/resolution scaler etc please don't combine all these settings to just one or two options i.e. deferred AA or post-processing AA, I'm looking at you BF4!
different options for ambient occlusion settings: No SSAO/SSAO/HBAO/HDAO
we should be able to scale down the polygon complexity of the models or any object in the game world
if they somehow manage to get screen-space reflections in the game, and actually put it to good use e.g. using on shiny surfaces, blood pools, when it rains, I'll be very grateful
and things from GTA IV should make a comeback such as draw distance slider etc
we should be able to turn on/off whatever extra sh*t they put in
oh, and please for God's sake let us turn of extra post-processing effects like depth of sh*t, colour blind or motion f*ck
I guess that's all.
For gameplay improvements, here's what I'd like:
car handling! (I'm not giving up just yet)
decent amount of gore, should be more than just bullet wounds or simple blood splatter
that's it for the gameplay amendments, the gameplay was never the concerning factor for any of the GTA games.