Revealing private key holding team members will only make the exchange less secure. This has been explained a million times in the replies in this thread. If you don't want to invest in the pre-sale you can simply wait till the exchange launches before the ICO then decide.
That's what they say? They are concerned that they are unable to secure the funds of their company? What are they noobs or what? How did all the other ICOs do it?
How dense are you people? I mean really i don't want to be an asshole but it is like you people put 0 brain power into thinking these things though. Most ICOs have no problem revealing their team because the crypto they hold is theirs, if they lose it it is their own fault. On exchanges they hold not only their own but all of their clients too, which means that not only do they have vastly more crypto but it is not their own, and losing customer funds would result in a lot of mistrust for the exchange and loss of clients.