This is less complexity than all of the yammering for sub 1 difficulty coins and vardiff. This feature request does not affect mining in anyway, and any database that can't handle a few additional fields per record is junk anyway. The only complexity is additional work for WP (which I admit would not be insignificant).
Must say I'm surprised by the negative response to this. Perhaps more posts complaining about vardiff, payouts, asics, BTC/MH, or stats would be preferred? Maybe I'll just go look for answers on the last couple pages and post questions as if I hadn't seen them.
Do you not see how complicated it would be to implement? WP has no login system, so how do would you confirm what coins you want to not trade?
WP has better stuff to work on, IMO. If you want altcoins, go mine them or buy them with BTC. If you want the best profits, paid in BTC, mine here.