I took this up recently at AOPA. Martin assures me that they have workable proposals.
Workable for whom?
I don't care whether they bring out a lightweight Mode S which works off a battery. I don't see why it must be mandatory for all aircraft at all times. It's overkill.
The only 'workable' solution is not to make it compulsory in absurd situations. Law makers have long recognised there is no point making a law which is both universally unpopular and more or less unenforceable.