If you want to use swords, i would download a mod that fixes their scaling as they become useless after mid game.
Obviously get all of the long war ish mods.
ShowMeTheSkills is a great ui improvement
The mentioned Gotcha is good for showing flanking stuff.
I recommend getting a mod that fixes AWC perks. They are hugely quirky and i remember not getting them on soldiers if i got the soldier before the building, which was dumb.
Also i recommend voice mods. If you like other semi popular video games or movies, having your favorite characters voicing your soldiers can be fun.
Also recommend Height Defence Bonus. I got real tired of my sniper on a high roof and behind cover getting picked off from someone on the ground like he was standing in the open.