So Meridian, being Meridian took the hardest challenge imaginable: SuperHuman Diffilculty, Hawaii Challenge. My hat is off to him, and I still don't know if its doable. If anyone can do it, its him. He makes this game look easy.
JStank tried to cram every mod together that he could get to play nice, to show off all the cool toys in OpenXcom, and his series is really good.
I saw a lot of balance issues there, as the "Get Sniper Rifle > Snipe All The Things" mechanic, can be quite hard to avoid. This is a possible problem with many one-off mods. "I wanna build the coolest, baddest, weapon, ever and destroy all the things!" >> can lead to OP tools.
I was going to go with a straight, non-modded OpenXcom series, but it felt like that is something that anyone who knows the Ufo Defense might already know, because it is such a classic. Not being the masochist (nor even a third the skilled player) that Meridian is, I looked for a way to change up from the standard track:
"Get lasers >Shoot all the Things > Get Armor > Get Heavy Plasma > Shoot all the things > Get PSI > PSI all the things > Go Blow Up Mars"
I hit upon the idea of Pistols Only. This is not a new idea, because I enjoyed a series called "Pistols/ER Only" of the 2012 Xcom from Coto Company, and had a ton of fun watching him beat that game with those limitations. It got me thinking about doing a scenario like that and what mods might be useful. The "Up Close Modpack" was born and I have launched the "Lets Play OpenXcom: Up Close and Personal" series, and have been really enjoying it. ("Long Guns are Bad! Pistols/Grenades/Melee Only")
Getting back to your original question: What are some good ideas?
One of the most engaging total conversions out there is Piratez! It has not been covered by a good LP. It you are up for it, I'd love to see it more than just casually reading the thread. Its almost a new game, so it may not fit what you would be interested in doing.
If you wanted to do pacifist, I have a decent collection of non-lethal gear in the upclose modpack. Three melee tools and three types of throwables.
A different twist might be "
Blow them all Sky High" ~ Can only use HE Weapons: Grenades, etc, Cannons, Rockets, Blaster Launchers. This would make live captures pretty tricky, and would cause some resource starvation, due to items being destroyed in successive blasts. I kind of like the sound of this one.
May try it myself, sometime.
Bottomline, though, Play something you will have fun with. Even a Vanilla OXC run can be hugely entertaining!
Cheers, Ivan