Been thinking about that.. but taking the price of creating a chain it would be just fair to keep them - yet as you say, remove the blocks.. my idea was again to keep rigs (of course, they are paid now.. it would be unfair to remove them!)and chains but remove all blocks of all chains.
I would stop the mining thread for at least 24hrs and give everyone the same chance of entering the game when the day comes to put up everything and then i would release the mining system again in order to have everyone start at the same time.
This is of course not a big bonus on the beta users, one may talk about just removing some of the blocks instead, but it would still give them an advantage on mining power..
Also i think about adding sort of an referrer model for the start of the game.. yet i dont know yet what to implement as bonus. The thing is, that such a game works best when many people use it.. and although i hate referral systems i think that it is the easiest way to get many players to start with.. so.. what comes to my mind as easiest solution is that people that invite (or something similar) new players may get an extra rig/upgrade? for every user they bring into the game (and who deposit.. or something. it must be fraudproof of some sort..)
But as it is just two days with no major bug being reported in the exchange it is too early for me to really start thinking about the final release.. i want to make sure that fucker works as well as have some other stuff implemented first..