All they really have to do is make a second blockchain to get tagged onto the first.
Just like a pointer, which points to a memory location, the last block of the current blockchain can point to the next one.
It could transmit the difficulty rating, and double the number of bitcoins.
I doubt 21 million coins will be sufficient to do a huge amount of commerce with. It will be a decent amount of commerce but not necessarily sufficient.
I doubt it's technically that hard to do.
You think the solution is to continually inflate bitcoin?