What era is this regiment for? You'll need 1 mech tech for every battlemech and the four astechs for each mech tech. My advice is to check out MegaMek HQ since it has everything you need to create a new unit from scratch.
Basic 3rd succession war, accept no other era, but it shouldn't be that different era to era. Clan TOEs are pretty disappointing anyways, since nobody who's not actually a Warrior appears on them.
And here we have, ladies and gents, a fellow who did not read my words. I have, in fact, got more than enough Astechs, because I gave each Tech six of them, off the top of my head because 7 men is a squad-size. Boilerman did a good effort, but man, there are assumptions I do not agree with in there-I want more support personnel than he does generally.
This morning(wow I forgot to post this for almost 10 hours), I'm gonna handle transportation. Let's start with the basics-1
ammo carrier, per lance, with a crew of 3, 1 similar sized general purpose cargo truck per lance to carry armor and replacement myomer, 1 modified truck, bus or APC devoted to moving techs around per lance, 1 coolant truck per company (supposedly there should be six for the entire regiment, but man, that is not a neat unit.) 1 mobile repair platform per company or if mobile repair platforms aren't available, a platoon of vehicles like cherry pickers, cranes and other repair aids may be substituted. We'll say that's 4 vehicles with 2 crew each per company. Total of 40 ammo carriers, 40 trucks, 40 apcs, 10 coolant trucks, and 40 assorted repair aids. Adding their crews all up, we get about 120+80+80+60+80=420 men. And we're not quite done yet.
We're also probably gonna need some other vehicles, to support the rest of the regiment, so let us be sure to include at least one MASH truck, three ambulance VTOLs, Five mobile field kitchens, and an extra company each of people-movers and cargo vehicles. We also might want an engineering detachment, and a salvage detachment, call them a company each. And for good measure, we'll make that a long-company for the salvage detachment by including a lance of IndustrialMechs in addition to the 12 Battlemech Recovery Vehicles. The MASH has about 20 people needed to staff it properly, the ambulances each need a pilot, co-pilot and two paramedics, the field kitchens require 9 cook and assistants each, 24 extra trucks with 2 drivers each (to prevent fatigue related accidents), 12 engineering and bridging vehicles with 2+ crew each, 12 recovery vehicles with an unknown level of crew, and 4 industrial mechs. Call it 189 crew all told for these guys.
We also have about 200 support vehicles, so we're going to need about 10 repair sections, each with it's own tech and astechs, for another 70 or so maintenance personnel. Oil changes, spark plugs, air filters, hell, they'll keep busy.
Fourth Battalion's frankly a huge monster, with 200 (mostly light) vehicles, and 679 personnel. But if you want to operate without the aid of dropships shuttling forward each time you engage the enemy, it is probably a monster you need to accept.
So . . .
In a combat unit, the HQ and support elements still get combat vehicles per TO&E . . . for instance, my unit was getting ready to go to a sandy place in 2003. We had all of our launchers, the trucks & humvees but we also had assigned to the company level HQ a pair of theoretical Bradleys. During field operations to prepare, they literally stuck a sign on the side of a hummer that said 'Bradley' for practicing with a QRF & movement. The APC with its heavier armaments was to be a security element for the HQ platoon- which at that time had mechanics & cooks assigned to that level. The BDE doctrine change later on had the cooks & techs assigned to BN but then parceled out like the medics.
Jeez man, are you saying that a company of battlemechs aren't enough security for the HQ? I'm making a straight battlemech regiment here, I'm not gonna throw in some tanks to guard the HQ vans. Nor am I going to give all the trucks which service the battlemechs their own Mechs for protection. I may be misreading you here because this is kinda a rambly story that doesn't actually convey much information to me, but this doesn't seem to actually be all that useful, unless you're suggesting that the entire 'combat' unit should be broken up and evenly distributed across 5 or 6 battalions.