Ehm, sorry, it cannot be done by 68k processors because they're too much slow, maybe for PowerPC, but one Amiga Developer (Guillaume Boesel) has tried to convert it to Ubuntu PPC (for Amiga X1000) and it doesn't work properly. I think it needs to rewrite many parts. :/
As I wrote somewhere it may be a way to support our community (for example "paying" developers/artists/translators/testers) and advertise Amiga platform outside its "niche marketplace". 
I ment if the mining was totally rewritten to be made for 68K as in complexity fitting the hardware, I understand that as it works now it's way to complex for the 68K CPU's but making new mining system based on 68K and then 68K natively only (so not people could punch out extreme amounts of blocks mined on emulators etc) would be possible but a lot of work and then it would be interesting for me since only Amiga users would mine then.
I know it wouldent happen but if it was going to happen I would mine with my Amigas
Beside if it would work as mentioned above I am no fan of any of the crypto-currencies and wouldn't use any of them.
