Risk / Comfort / Convenience will drive this individual decision.
If I decided to replace the cushion with the chute, I could probably pad it and make it a little more comfortable, but having the chute properly strapped on inhibits some movement and gets uncomfortable after a while.
Then I have the difficulty of strapping it on (and taking it off) when I get in / out of the plane.
ALSO, If the chute is in the plane all the time, I would definitely want to keep the chute inspection records up to date.
If you really wanted to do this, I would go all out and replace the seat belts etc with a custom made chute/harness assembly. The chute harness now becomes your seat belt assembly. You'll see these in some of the professional acrobatic planes, i.e. extra 300, etc.
Waiter