IS characters:
- Beanstalk and Purestream E2 for IS5
- Angelina Module for IS. It's a busted skill and she has a good uptime.
- Gravel E2 if you want a better temporary blocker (although I rarely see her used anymore, I used her in IS5 Ending 4)
- Kroos2 for IS4 (passive stun is really useful)

- Crownslayer once she gets her module for perma-stun shenanigans
- Civlight Eterna but only if you want to use her S2. I've seen some cool clears (like against Lappland boss). But if you use Skadi alter a lot, no need.
- Ethan S2M3 + module. Better than any defender.

- Mostima S3M3 with module if you want full map slow shenanigans
- Narantuya is a fantastic DPS. Unfortunately for her she has a lot of competition among snipers but after Wisadel, I find her the most flexible
- Stainless for better-than-warfarin buffs. You want him if you want to see big numbers

Nice, you have a pretty well built account!
Honestly you are at the point where you can build whoever you want since you have all of the good DPS ops. Now, you can invest in niches that find rare use cases. Few examples:

What's your current set of operators? I can give you a recommendations on who to build if you can screenshot/krooster everyone you have.

Reminds me of Reverse 1999 in art style and how that game doesn't always use humanoid characters.