Is there any mechanical reason the BRS system could not be designed to allow
the chute to deploy, stabilize/slow the plane and, optionally, allow the
pilot to disconnect the chute to land normally?

I'm thinking about floating down in a $400K Cirrus with chute deployed in a
spin in IMC, then breaking out at 1500 feet looking at a suitable landing
place and cursing the imminent destruction of the plane.

Michael