Couple things to guide you: Standing Guard units are typically brigade strength (ie: 2-3 regiments), equipped with usually a company or less of Mechs and high in regular infantry and conventional fighters over BA and ASF.
Things change too - the above is from FM: 3085. I imagine by the early dark ages you’d see even less Mechs, but maybe an increase in BA as they become more common.
And the when the HPG link goes down, I’d expect militias to rush in more and more converted WorkMechs.
So it really depends on what year you’re thinking.
I’d suggest backing up your command lance with a lot of older gear cast off by the regular troops, a smattering or RetroTech designs like the Rook, etc.
And then round that out with a couple AgroMech MODs or something.
Maybe chuck your lance commanders in decent, newer machines like the Blade and fluff them as recently moved from regular RAF?
The good news is you can get some decent tanks like the Demon (both older assault class and newer Medium), some Marksman MBTs and decent BA like the Kopis and various Purifier knock offs made by the RAF.
Oh, and what about some Condors for your light cav?
