The Cirrus strops actually attach to the top engine mounts aft of the firewall. An interesting point is the strops are supposed to be replaced every 10 years (IIRC) so there must be some early Cirri coming up to needing a fuselage re-glassing and respray when the strops are removed unless they can be removed from inside, or pulled through.
Another problem is for the fire and rescue services - working through the doorway of a bent Cirrus fuselage with a potentially unstable rocket and the strops running underneath the doorway.
The C150 with a BRS fitted was shown on video demonstrating how hard it would touch down. The bottom of the fuse hit the floor, that's how far the gear legs bent. Cessna 150 seats aren't built the same as Cirri ones....
The weight of a BRS could be used for 10 gallons of fuel and whilst there no doubt are times it would save lives it isn't the toal answer. For instance, structural failure? Best you hope the failed structure (broken wing) isn't going to stop the rocket, parachute and lines deploying and behaving as advertised.