might be, but this would not only be a hard fork: all the miners would have to be updated too.
if we only added the superblocks, those mining in a pool wouldn't be affected - only the pool server would have to update the riecoin client.
You are proposing a more aggresive move.


We would need a difficulty of 1060 (in 7-tuples). Current computing power (1462 in 6-tuples) would translate to a difficulty of approx 705 for 7-tuples. So changing block time to 4 minutes (or having 4 mins superblocks) would do the trick. If we had 4 min blocks we would find a world record size 7-tuple every block and a record octuple once or twice a week. Some years for a nonuplet, but it would be one hell of a nonuplet, exceeding current record by orders of orders of magnitude.
edit: I'm tired, my math is shaky... it's not 4 minutes, it's 2 hours. Still doable with superblocks, but forget about finding nonuplets - or octuplets - this way.

If we were going to change the PoW in such way, we'd better make it accept alternatively 7-tuples, 8-tuples and 9-tuples each with different difficulties, so we could easily break all records every day.

I made a lame attempt at giving room for this kind of change in the future by adding a "primes" value hardcoded to 6 in the "getwork" and "getblocktemplate" calls, thinking that maybe in the future this could be variable. But the thing is that we would have to update all the mining software, and see which patterns we would look for, not only the number of primes. So we would have one block be 6, the next 7a, then 7b, 8a, 8b, 8c, whatever, then repeat.

edit: looks like for 25-tuples, there are 18 possible patterns all with diameter 110... I guess we wouldn't go that far