Firstly, this is just a bandaid for the real problem (the real problem is that importing a large inventory with lots of product variations is cumbersome and not user friendly). That being said:
It would be great to be able to run a CSV through a validator and see ALL of the things I need to fix.

Currently it goes
Upload file>Map Fields> No! This is Wrong!
fix file
Upload file>Map Fields> No! This other thing is Wrong!
fix file
Upload file>Map Fields> No! This is OTHER Wrong!

And so on.
If you could just return all the errors at once, at least I could go and fix them all instead of waiting so long for the thing to validate every time i try to import.