Am curious to hear people's opinions on this (especially ex-service members as they'd have real world experience).
I wasn't a logistics puke, but I was a staff monkey, so I'm at least familiar with the ins and outs. In the military, "big Army" isn't going to send you anything you didn't ask for, and priority of supply is going to go to the units that are most likely to be in combat. If both 10th Marik Militia (garrisoning the CapCon border) and the 1st Regulan Hussars (stationed safely deeply within the FWL) both submit requisitions for SG LRMs, for example, the Militia is far more likely to get them than the Hussars. If a unit is on orders to launch an attack, they will get the highest priority for shipments of supply of any kind because units in combat go through their consumables at a massive rate; I'm not just talking about ammo here, but also fuel, POL (petroleum, oil, and lubricants, which includes things like anti-freeze for ground vehicles), and food (both field-kitchen "cookable" food and MREs).
In the politics-is-life FWL, perceived loyalty is also going to dictate how much support you'll get from the Federal government, as even Thomas "Marik" played favorites and punished dissenters by playing with their supply shipments. If anyone is going to have SG LRMs, it's the Knights of the Inner Sphere, and if anyone isn't going to have them, it's the Regulan Hussars. I'm sure other BT militaries have similar issues; the LAAF under Katherine was more likely to give good stuff to the Jaegers brigade than it was to the Skye Rangers.
But back on the real-life train! One more thing to mention is that small-batch orders are more likely to get filled than big-batch orders, because it means you're not stockpiling, you're using them for training (and troops need to train on new gear and munitions so that they know what they're doing with it when the bullets actually start flying). Requesting five hundred tons of SG LRMs? Unless you're on the schedule to invade Corey or Bolan, not going to happen. Requesting fifty tons of SG LRMs for training? Sure, some warehouse on Marik or Oriente probably has that lying around.