As a PC Player what do you think of campaign or character starts that are different than you were lead to believe/understand/expect?
As a Player, I think it depends on what happens.
As a DM, I think it can be a wonderful opportunity to create a world of surprise and adventure. I have done the Gilligan's Island/Lost story on PC's before, and it was generally well-received.
After considering it for a few minutes, I concluded that had it been me and my character, I would have told the GM I didn’t want to play that character.
Well, without seeing the results, it's hard to say whether that'd be justified or not, but I would point out that there's a benefit to rolling with the punches, you get a chance to do something different that you didn't expect.
But then if I were the GM of that game, I might have said "write up your general character concepts" and then made characters for you, or even presented a sampling of characters to choose from.
Had you been the Player whose character’s “race” was drastically changed, would you have a problem with it? Or would you just roll with it?
Well, I'm obviously more familiar with the Warden and MA than you, so I wouldn't have been anything but suspicious when I heard the description, so I'm probably not the best to ask.
In this case, MA actually has a starting scenario for mutation of PC's in the cryo-chambers, so it wouldn't be something unexpected for me. Now did the GM change the character too far? I don't know, you didn't describe that fully.
And given how many of the mutations are helpful in the game, I wouldn't necessarily object too much without seeing it. Or the presentation. Perhaps if the GM had said "Ok, a radiation storm has hit the ship, would any of you like to roll for potentially beneficial mutations?" then you wouldn't be troubled by it.
Don't know, but it's good that even three decades later, some of the old surprises can still work. It's like using snakes in a can! Awesome!