Varies with each new AtB Campaign. Lately I have been messing with the AtB Noble Rules and customizing the scenarios to work on set land-hold maps.
I add +40 to each map's hex size in all other AtB campaigns. Chase Scenarios are on 58x110 maps.
Added on-board Artillery lately, and getting used to using it.
I tend to keep a flight of aircraft for CAS, or CAP if the enemy is deploying fighters. Fan of using a lance of Warrior H-7C for CAS too. Spot for indirect and park them behind a hill or trees. Hot-load a single ton of LRM Ammo for use with the SRM-4. Another unit to TAG and Semi-Guided works well with them too. I limit them to one battle reinforcement a week.
I use my support personnel in Base Defense Scenarios. This consists of infantry squads (Rifle Foot Infantry works, 4-man squad for admins, 5 for medical team, then 7-man squads of 1 tech and 6 soldier/astechs) and support vehicles such as cargo vehicles, coolant trucks, salvage vehicles, etc.
Noble rules I swapped the civilian units for light tanks, most of the same rules apply including limited lance size by terrain type. These and their personnel are tracked by the unit in MekHQ. They can be replaced with heavier units, but overall lance weight cannot exceed the land-hold battle weight. i.e. Light lance for no facilities, Medium with facilities or an urban map, Heavy if it has both.
Toying with the idea of setting the difficulty to Elite and then using a combined-arms company per scenario. Basically a Battalion overall. Only one lance per company is set for a scenario type Defend/Fight/Recon/Training. The other 2 lances are the reinforcements. One lance of mechs, one of vehicles or infantry, and a support lance of artillery, transports, etc. None of the lances can exceed the weight of the lance assigned the role type. Start with only a single combined-arms company.
Finding I like the FM Mercs Personnel Market better for Noble AtB. Never off-contract to search for certain personnel. Only rolls once a month, but you get a bit of a choice of who is available. Not always good choices. Lost a couple aero pilots after they lawn darted. Was months and moths to get anyone regular or above in the market.
Planetary Availability Market is working great for Noble AtB. Noticed things like Clan tech is a lot harder to come by even in 3070 Federated Suns. Was too easy to come by before. Just because you find a deal on a Clan mech on the unit market doesn't mean you will be able to find parts in a timely manner if at all.