DAAK has a pretty good LL system for AAR, it would need some modification for AA50 for reasons mentioned above (changed BB CA bombard rules, changes to sub rules)
I would agrue that for AA50 to BB and CA should fire with the ground forces and subs should only fire separately if no DD present, to reduce the variance.
DAAK use an SBR table where the attacker loses 2-3 IPCs (50% chance for each) per turn, from your starting cash pool (as in AAR bomber loses 2.5 IPCs on avergae vs AA gun [cost $15 in AAR]) and inflict 2-3-4 (33% each) IPCs damge to an IC in a 6+ territory since bombers inflict on average 2.92 IPCs per SBR vs AA gun. If no AA then attacker loses nothing and inflicts 3-4 IPCs (50% each)
Different damage tables handle different scenarios (max IPC caps for terrirory value and also with/without AA firing).
Pretty annoying for F2F games though, I personally prefer LL online but ADS in F2F since the calculations really make a live game drag on for ever and ever.