Sorry if this is treacherous heresy here. I know very little about WH40K.
I love seeing your minis and the collecting aspects. I wonder if there are cooperative alternatives or forms of these games, as my partner and I are not very competitive people. We enjoy expressing ourselves with our choice of… Idk, armies in the case of 40K, I guess. It’d be nice to find a system using minis that would allow cooperative gameplay, as I don’t fancy collecting a buncha minis, and leaving them to sit. At the same time, I’m not creative enough to construct my own game system to meet these needs, so an existing structure would be nice. Thank you, Mini Masters. 🙇
There’s also Five Parsecs from Home, which is a solo wargame / RPG. You only need a handful of minis, and it’s miniature-agnostic so that you can use any mini you want.
Hey! You should look at Blackstone Fortress it’s set in the 40k universe and is a 1-5 player coop game. You’ll get all of the minis to play the game, no more no less, so there’s not really room for growth but I believe it’s in the same vein as Gloomhaven.
You could check out Kingdom Death: Monster. You could use many of your 40k minis as your survivors, and it would come with a ton more minis to build and paint. Alternately, you could try to find somebody selling the game for cheaper without minis, and only use 40k minis in the game.
There is this thing being developed for you to fight solo/co-op against a huge swarm of Tyranids, it might be of interest! https://www.goonhammer.com/fury-of-the-swarm-the-40k-co-op-open-beta-begins/