A Random HECU Fan

I’m trying to model the HECU in scratch but I can’t decide if I want it to be game accurate or not. Everyone tell me their preferences for the HECUs design (historically accurate, game accurate, other; please specify, etc.) so I can get some ideas and hopefully stress out a little less.

Does anyone know what Gas Mask the HECU on BM use? GPT said a modified M15 but a Gas Mask wiki says Half S10. I think they're a german type but i dont exactly know. If anyone could help me it would be greatly appreciated.