I agree, one profile for each chaos divinity + 1 generic profile would be interesting. But avoid the weapon selection, defiler is smaller than a titan

About your profile proposition, I'd say:
- making it a Possessed Daemon Engine is fine
- Defiler Cannon: -3 ? Really ? This seems a bit overpowerd for a so small cannon. I don't have the feeling it's better than a bone-crusha cannon. 4+/- 2 would be slighty enough.
I based the following stats on your propositions that were interesting. Chaos powers are the standard ones (no need to create/modify them).
Chaos Marine Defiler15cm, 4+ all around, +3 Caf, (Possessed Daemon Engine)
Common weapon: Defiler Cannon 50cm x1 4+ -2
Khorne:- Tentacle things  -  -  -  -  +3 Caf
- Heavy Flamer Flame Temp - 5+ -1 (Ignore cover, Fire*)
- Berserk:May not have First Fire Orders. If Chaos is winning: +1D6 CAF, +1 Armor Save & To-Hit rolls.
Tzeentch:- Twin Lascannons 75cm x1 4+ -2
- Havoc Missile  50cm Temp 5+ -1 (6cm Temp, Artillery, Ignore cover)
- Warp Focus: +1 Chaos Reward Card at the start of the game.
Slaanesh:- Reaper Cannon 50cm x2 5+ -1
- Havoc Missile  50cm Temp 5+ -1 (6cm Temp, Artillery, Ignore cover)
- Glamour of Slaanesh ( -1 to hit modified, 4+ Psychic save)
Nurgle:- Reaper Cannon 50cm x2 5+ -1
- Tentacle things  -  -  -  -  +3 Caf
- Never outnumbered in Close Combat.
Undivided- Twin Lascannons 75cm x1 4+ -2
- Tentacle things  -  -  -  -  +3 Caf
Maybe the undivided could cost 150/175 and chaos divinity versions 200/250 ?