I was reading more suggestions regarding life support and thought "Why are we considering Kerbal life support before we consider Kerbal crash protection?".
Right now we can subject our Kerbals to rapidly oscillating 15g accelerations along multiple axes for indefinite periods of time without killing them. This is silly.
We should have our Kerbals black out/red out at 6g of normal or anti normal acceleration depending on Kerbal seat or capsule orientation. A blacked-out Jeb no longer provides pilot SAS. At 12g our Kerbals should not be reviveable until the craft is recovered.