I don't really see the Blade as an AA 'Mech. A light support to be sure, and I'd strongly prefer to trade energy weapon range for increased AC power, LAC/2s are just kinda lackluster. With my twin LAC/5 concept, i'd probably go for AP, precision, flechette, standard as ammo options, though specifics would vary depending on the scenario and expectations about what enemy will bring, of course. Run around, slowly add some damage to 'Mechs, not unlike the Rokurokubi, possibly deal with infantry where relevant.
Of course, i don't play with air power, except maybe battlefield support stuff from BMM.