Mentioning 2^N variants on this specific proposal is probably the worst place to do so - Zca, Zcf, Zcd are all subsets of the 'c' extension, and Zcmp is incompatible with the 'c' extension, which severely cuts down the combinations - having the 'c' extension, which Linux expects, makes all (but Zcb I think?) extensions here either implicitly supported, or incompatible.
And, given the scope & purpose of these extensions, most things (distributed binary programs, OSes, all but a few compilers) won't need to use nor care about these. The alternative to these extensions, to those that need them, would be either suffering decreased performance/increased ROM size, choosing a different architecture, or making proprietary extensions (at which point you could have multiple vendors with incompatible extensions doing the same thing) - all of which are bad alternatives.
And, given the scope & purpose of these extensions, most things (distributed binary programs, OSes, all but a few compilers) won't need to use nor care about these. The alternative to these extensions, to those that need them, would be either suffering decreased performance/increased ROM size, choosing a different architecture, or making proprietary extensions (at which point you could have multiple vendors with incompatible extensions doing the same thing) - all of which are bad alternatives.