If your concerns are that you don't yet have the experience for a lot of design work (but you do have some money to spend) then PURCHASE A DRIVETRAIN, instead of designing one. VersaChassis is great but you still have to machine it together, make sure all your distances are correct, source the correct length belt/chain. Using the
AndyMark pneumatic wheel upgrade kit as a guide for what to buy is a great way to go (or just buying it if it comes back in stock). We were very successful crossing defenses using that kit by simply slapping an angled plate on the
front of the robot. The 1/8" drop center distance was perfectly adequate after we under-inflated our outside tires.
If cost is really an issue you could try to reuse an old LOP drivetrain (or even this year's if you have it!).
As you learned this past season, the drivetrain is the most important part of the robot, without it you can't do all that much. Focus on putting great things on top of the robot rather than mucking around with the most important part. Next year you will likely be able to use the KOP again, and once you have stronger design skills, you can start building your own drivetrain.