In "the olden days" the Altcoin Discussion forum here at Bitcointalk was quite a good place to discuss these topics. While Proof of Stake was proposed
here in the Development & Technical Discussion subforum, the concept is from 2011 and thus predates the altcoin subforum, and discussion then moved to the altcoin forum once it was established.
If you go
back to the first threads in mid-late 2011 in the Altcoin forum, while there were a lot of threads about specific altcoins ("SolidCoin" for example, and NMC, later LTC), every now and then some (crazy or less crazy) ideas popped up, like
this or
this. I believe also the concept of "Stablecoins" originated there.
I would appreciate a subforum "Blockchain technology" or "Cryptocurrency technology" for all threads about technology not specific to Bitcoin but also not specific to some altcoin. This could even increase the relevance of this forum for the non-Bitcoin crypto sector again, because there seem to be few neutral and high-quality spaces to discuss these things. The only other place I really know is the
CryptoCurrency Reddit. And maybe Altcoinstalks but what I've seen there was much shallower.
Personally I have no problems with such threads showing up here (as long as no shilling is involved) but some seem to do.