So this year the Pigmice are shooting for changing how we design our robots. Last year is a perfect example of why we want to change. The robot was the most complex on the field, and it weighed 19.99 pounds (actual weight was probably 120.3).
The robot is shown here.
Although everything worked and we almost won a regional, I’d like to see us take a different approach. Specifically “Simplify and add lightness”.
Any ideas on how to approach this.
CAD everyone before you build it, if it unnecessary take it off. I see you guys did a swerve drive. Which does add a lot of weight and complexity, maybe go with a 6 wheel drive.
But if it works, it works 
Also I assume you mean 119.99, i wish you could build a robot that is 19.9…
For weight, you can start by using lighter materials, like the plastic pneumatic tanks or 1/16" aluminum extrusion. You could also sacrifice your swerve drive and switch to the lighter 6/8 wheel tank drive design (which would be sad because swerve is cool). I also really like this paper which is about lightening a robot after it’s built, but still has a lot of tips that are valid in the design process, too.
Designing for how you plan on playing the game, and not all posibilities.
You built a great robot from the video. What it looks like is you approached the season as how do we solve the engineering problems, and not how do we play the game best. Never forget the KISS principle. Your grip tubes great, but there are simpler methods to hang with the stats your video bragged about
^^^ True that, That’s why we are looking to change some things 
We have recently bought fiberglass tanks (5 of them), with the idea that we might be able to ditch our compressor.
We have also begun placing more emphasis on CAD.
As for KISS, swerve is most defenitly out (kind of a shame, but we are replacing it with a fully modeled WCD).
The tricky bit will be keeping our manipulator simple.
As for manipulators. Are there any golden rules that you can think of?
For manipulators, make sure you think out all of the small details in the design. In 2010, our kicker was VERY simple, but a few very small issues caused that were never thought about caused it to never work. In 2011, we stayed simple with a folding arm, but we thought out every little detail and it worked great with very few issues.
Design for your strategy to play the game. If it weighs 119.999999 pounds then so be it.
Some one once told me, design is iterative, once you learn a good iterative design process you can work wonders.