Reminds me of the Alternate Story Series (http://elementscommunity.org/forum/index.php/topic,20252.0.html). (Currently Archived by me until I find the time and energy to revive it.)
Also, thanks to the above series I've seen some serious flak get thrown at the idea of alternate upgrades. How would your method of coding the "luck-based" upgrade work?
Ah... I didn't know anyone else had thought about Alternate Upgrading ^^; Didn't mean to steal your idea there. But I thought of this idea more like Shadow Pokemon from Pokemon Colosseum DX. I think, anyway. i never fully really playing that game ^^;
It's fine with me. (Funny thing is that I was just thinking of reviving this idea and then I saw this pop up.)
Actually, this could be collaborated - Alternate Story Upgrades could be sort of like the normal "Alternate" upgrade with the option of choosing (having some sort of requirement to unlock the alt upgrade), while Underground Upgrades could be the "Dark" variant that's a little chancy to get but could be accessible from the start.
....Dang, I now have some random gimmick ideas on how to make my Alternate Ideas get special upgrade methods.
*Sits back at drawing board and takes out a file labeled "Alternate Upgrades"*.