Ran into an interesting problem in trying to use the MUL to determine forces for factions they don't actively track, including Niops: the IS General and Periphery General lists aren't fully inclusive of all general items. It's talked about in the following two posts:
https://bg.battletech.com/forums/errata/master-unit-list-mul-feedback-thread-iii-read-the-first-post/msg1912339/#msg1912339https://bg.battletech.com/forums/errata/master-unit-list-mul-feedback-thread-iii-read-the-first-post/msg1912349/#msg1912349and to a lesser degree here:
https://bg.battletech.com/forums/errata/master-unit-list-mul-feedback-thread-iii-read-the-first-post/msg1912442/#msg1912442To summarize: some units on the MUL like, say, your typical 28-person or 21-person infantry platoons are
not on the Periphery General list, because factions like the Taurian Concordat and Marian Hegemony use non-standard sizes for their units. So any units not specifically shared across all Periphery factions, including ones that use non-standard unit sizes, won't show up on the Periphery General list at all.
The difficulty: the Periphery General list only tracks units that all Periphery factions tracked by the MUL use, and Niops, along with other small Periphery factions like New St. Andrews and Randis aren't tracked. Thus, there are significant gaps in some areas of the list if you're playing one of these factions, notably in areas like infantry: if you don't like Tariq-mounted infantry, you're out of luck - the exoskeleton suits like the Groundhog that show up on the Periphery General MUL are for the base suit, not for the suit equipped into squads of any particular number.
This shows up in other ways too, though. What's New St. Andrews without the Arbiter? Out of luck, because the Arbiter is only on the Inner Sphere General list. Randis has the Periphery General's HWK-3F HawkWolf, but gets denied their HWK-4F upgrade, because the MUL only has that down for the Taurians, Calderon Protectorate and Fitvelt - it's not on the Periphery General list.
Why does it matter? Because just like some games prohibit custom 'Mechs or other units, some games require you to take units that are specific to your faction list on the MUL, and because they're not actually tracked, you can't get a really accurate list of what those factions use from the MUL.