One major challenge for sailplane BRS systems is water ballast.

If you size the BRS system to the ballasted gross weight, you end up
needing a rather large system that costs a lot and takes up a lot of
internal volume.

On the other hand, if you size the BRS to the dry gross weight you
have a system that is overmatched under many flight regimes, including
many in which BRS capability is most desirable - such as climbing away
from a start at a crowded contest site.

You could placard the system into compliance with a sticker that says
"Dump ballast before deploying BRS" or "Do not deploy BRS while
ballasted." But that doesn't address an important issue: most ballast
dump systems can't empty the water out in less than about a minute,
and some take as much as three or five minutes.

I suppose the savvy glider developer could also embed a steel cable
into the wing skin, and tie it into the BRS harness so that deployment
unzips the wing and liberates the water. That'd be a sight to see.

Bob K.