Glad to hear you like the game!
A sort of "endless mode" idea has been brought up before.
Something similar was actually planned to be in this game, but the idea was scrapped in the end.
While I'm not opposed to such a mode, I usually don't believe in updating my already released games with new content.
On top of this, there are other things I'm currently working on at the moment, so it seems that for now the idea is on hold.
I appreciate your interest, though. Thank you. :)