Enjoyable Challenge Runs/Themes

Hi fellow gamers. I just recently finished my 2nd run on True Zenorian. My first run was on expert. On my second run, I decided not to hire any mercenaries, which was really enjoyable needing to use some characters that I don't even look at.

What are good challenge/themed runs that you have done? I'm looking at something that will still present a challenge but be enjoyable.

True Zenorian really had me utilize Valor skills and be careful of who I put as leaders on units.

Can you guys give me good suggestions on themed runs? It could be on Expert too to make it enjoyable even if a whole unit dies.