[Billfred]

A few thoughts:

1) I've hung banners with thoughtfully-designed robots done with a measuring tape, angle and box aluminum, and pop rivets. I've had well-CADded and waterjetted robots miss the show. There's no magic bullet here.
2) Knowing your fabrication resources is instrumental to making any CAD work. If you can't buy or lathe a shaft to fit an application, you shouldn't be putting it in the drawing! If your machine shop's tooling has a minimum radius on cuts, make sure your lightening pattern's corners have at least that radius! Start this conversation now, and do some smaller-scale tests before betting the farm.
3) Part of legit-ness is having time to practice driving. Can you turn around a drivetrain that fast, and is it that much better than the kit drivetrain (or the kit drivetrain with some bolt-ons)? Do you have means to keep old robots together and running so the drivers can get some stick time in before this robot is together (and some time against defenders afterward)?
4) Another highly underrated part of legit-ness is just not dying. Did your robot break down this year in a match? What happened there, and how can you fix it on the next robot?