I must have read it here or maybe in another BMW topic, but who came with the idea to put the 3 bearings in the centre of the crankshaft on the BMW-139, was it BMW or demanded from RLM? Did the Bramo-329 had the same bearings arangement, or a normal one, one centre and one at each end?
Otherwise, a better BMW-801 is either one that appears earlier by having Bramo and BMW merge in 1936, and the combined effort and expertise resulting in a successfull 801 in 1938-39 (one year early), OR a better BMW-801 is a... DB-603?
If the development of the DB-603 is not curtailed in 1937 or whenever it was, prototypes should be ready in 1938-39, powering Do-217, FW-190, maybe even the Me-210 etc. Initial DB-603 plan was for a 1500 HP engine, so power is basically the same as the 801, and would be increased to 1600 HP or so in 1940 and 1750 HP in 1941-42.
Being a DB it has better altitude performance, less drag being an inline AND runs on B4 fuel. The C3 fuel can then be used either to boost the Bf-109 performance (which badly needs it, especially the earlier G models), or to make the FW-190 even better with a 2000HP DB-603 with C3 in 1942-43 (!), and 2250 HP MW-50/C3 version in 1944.