I was thinking ages back, given the resources a Guard Commander can have to work with and/or alongside (units from Guard Codex, 40 technology, Spacemarines potentially, Imperial Inquisition), what would they do if an enemy army came at their world? Although all units have their use on the tabletop (some being better than others) this is conflicted by the differences between what can be done in fluff and the current set of games mechanics.
I'm curious as to how the commander would go about several things:
1) Determining who's attacking (the initial attack might leave no witnesses)
2) Where they have attacked might might target next
3) Where they are
4) How to find out their strengths and weaknesses (or any strengths and weaknesses)
5) What would be the appropriate counter
6) How to get your counter to where they are (transport / orbital bombardment)
7) How to determine if your counter has worked based on either complete or partial information
It's a big list, but I'm curious to see how someone given the resources would use them. I'm imagining it's a forest world with mountains and the enemy will turn out to be in both environments.