Robin
It may be a dead duck as far as gliders microlights etc are concerned but transponders fitted to those aircraft will at least allow aircraft fitted with TCAS to see them.
A white glider circling in one spot under a cloud is not very visible especially to a twin prop chopping in and out of cloud, IMC one second VMC another second.
Maybe it should be a choice to have TCAS but compulsory to have at least mode C transponder for all flying machines?
Pace