I'd love to do priv key import, but it cost isn't worth the usage. We won't ever import a foreign key into our wallets which means we'd have to set up a duplicate wallet for every coin. It just isn't viable. If you have an idea of how to accomplish it, i'm all ears.
As for forked coins, @blocktalk is absolutely correct. We either upgrade and follow the majority fork or risk being on a broken unsupported chain. It isn't about us supporting devs; its about us supporting the majority of users of any given blockchain.
If trex takes on a more professional look for traders like Poloniex does...I will switch to you guys just because I am from Seattle and want to see you guys do well...however I like poloniex UI much better as a trader.
Polo has been dropping the ball recently, just switched to Bittrex. Good so far, we'll see.