The more "automatic" controls you put on an engine the easier a pilots job is (and the harder the maintenance personnel have to work). You also have Murphy's law
I was thinking more in line with what was done on the DB-601 early war but applied to the prop controls rather than the supercharger. I suppose the variable speed supercharger control unit itself would increase failure rates and maintenance (and obviously manufacturing cost, complexity, and weight). Let alone the engine computer BMW introduced on the 801. (Bramo had previously used single-lever systems on the 323 -and I assume developed them for the 329- so there was a good degree of background work there already)
Having automatic limiting/control systems oriented towards avoiding catastrophic failure would probably be more important. (I'd imagine the V-1710's automatic boost control helped to some degree in avoiding detonation, at least on the 9.6:1 models -with 100/130 fuel it seemed near impossible to induce detonation even wide-open at SL at 3000 RPM, at least with a rich mixture; damage due to excessive power levels overstressing components would be less immediate and more related to intentional abuse or prolonged pilot error -or calibration error- rather than the rapid onset cylinder damage caused by detonation)
Aside from that, manual or semi-automated control on the pilots end should still be useful for higher power levels and not just cruise. Even prior to clearing engines for WEP ratings, more power (and better specific fuel consumption) at military rating below critical altitude and take-off would seem fairly straighforward. Manually operated variable pitch propellers would make that more difficult, but constant speed propellers should have simplified that a great deal. (2-pitch propellers would be a good deal worse but not really be a factor in USAAF use)
I'm not sure if all newer USAAF aircraft had adopted constant speed props by the start of the war, and I recall references to constant speed propellers on the P-38, P-39, and P-40, but that term is sometimes misused in the more general context of variable-pitch propellers.
It's possible that individual squadrons adopted unofficial ratings and procedures on their aircraft, but it seems far more useful to actually provide official ratings for optimal performance and practical procedures to implement as standard. (having pilots constantly checking boost and RPM during climb/combat wouldn't be practical, but setting lower RPM+high boost take-off procedures along with lower RPM mil/WEP settings in steps similar to those used for supercharger gear changes would seem more practical)
For take-off purposes (at SL), the V-1710-39 could manage 1325 HP at 2400 RPM wide-open at 50" Hg.
The older V-1710-33 chart has slightly lower power levels across the board (and also lists the supercharger gearing at 8.77:1 rather than 8.8:1; that doesn't seem like a rounding error given Allison tended to give values to 2 decimal points when applicable). I haven't seen details on the overall changes between the C and E/F series V-1710s, but I suppose there were at least some modifications to the supercharger installation. (though the V-1710-39 specification sheet also lists the -33 as having 8.8:1 supercharger gearing)
In any case, the V-1710-33's chart puts it at 1260 hp at 2400 RPM at SL pushing something close to 49.5" Hg.