Still haven't decided on a robot
My only suggestion so far is that I'd probably leave the 30+ bullet points of Robocode rule details / formulas for later, or in an appendix. It's going to be boring to a newbie, and without any context, they probably won't retain that info anyway. A few sentences of overview about robot/bullet capabilities would be easier to read and draw them in more. You can link to specific rules in the appendix from the main text as you go, if needed.
As for which robot, I think it's really hard to find any objective answer. I doubt anybody's that familiar with multiple top bots' full source code. And even if some folks are, it's a tiny data set to draw conclusions from. I still say that since you're so much more familiar with Gilgalad, it would take a really compelling reason for me to vote for any other bot. I do think Diamond is pretty well designed, and judging from Skotty's incredibly detailed write-ups of XanderCat, it sounds like XanderCat is too. I don't know that DrussGT is a bad choice, either, besides occasional comments from Skilgannon about how messy the code is.