Was the Bf110 inherently a bad design or could it have been a better fighter if executed better? It seems a common theme that aircraft in the period considered were good short ranged fighters or had decent range and were poor fighters. Extending range on the good fighters has a high price (zero) but could any of the twin engined ones be improved enough to make them adequate fighters? So reasonably competitive with a hurricane for example. Or is air warfare so reliant on small margins that nearly is nowhere near good enough?
Bf 110 was IMO a good design. Problem is that, when country/ministry/government invests double of everything in a 2-engied fighter (double the number of engines, propellers, airframe weight, fuel usage, manufacturing time, usually more crew and firepower) vs. 1-engined fighter, the resulting aircraft must be a great design. Or, in ww2 frame, it must be able to out-fly everything in the sky - and that was not what Bf 110 was capable once against the RAF.
Extending the range on 1-engined fighters was easy. A drop tank facility on a Bf 109 worked well, but it was too late for the BoB to make an impact. Greater internal fuel tankage was not just Zero's 'trick' (it was no trick), eg. P-40 in 1940 flew with 180 US gals of fuel in the internal tanks, the P-40B in 1941 flew with 160 gals. These were as fast as the Bf 109, topping 350 mph. The Bf 109E flew with 105-106 US gals.
Range can also be extended with good/great streamlining - the Bf 109E was not that good in that regard, the streamlined 109F was much better and was rangier on same fuel.
Back to Bf 110C - on same engines, it was ~70 km/h slower than the small IMAM Ro.58. Or, it was about as fast as the small Fw 187, despite having 50% more power. So if the Bf 110 was designed as a smaller aircraft (not bigger than the P-38 IMO), it would've been not just considerably faster, but it would've been lighter, a better climber and with a tad better range.
At the end of the day, for the German needs a big fleet of 2-engined fighters was an big economic burden both to buy and operate, they should've been better to go with a well-streamlined 1-engined fighter instead.