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The Hs124 would have stayed relevant as a night fighter and light bomber (with engine upgrades) for the whole war, while the Fw187 could have done the same as a long range fighter and daylight bomber interceptor, preventing the need for the problematic Me210/410 that ended up costing the Luftwaffe an estimated 2000 aircraft from 1941-43.
Early on you could have the Hs124 as a light bomber replacing some of the Ju88's roles, especially the Ju88C, and some recon versions, which would make up for the needed resources to produce it; it would also pretty much replace the Do17 in all its roles from 1937 on. There would be virtually nothing the Do17/215 could do that the Hs124 couldn't do better and probably use the same engines to achieve higher speed and range, though with lower payload. The He111 and Ju88 could then do the 'heavy' bombing. The Fw187 then would be freed up to be a bomber interceptor during the day and long range escort/air superiority fighter. In the long run it ends up saving a lot of resources from having to switch over to the Me410 when it becomes ready in 1943 and avoids having to go through the Me210 fiasco, while the Bf110 doesn't get wasted during the BoB, which the Fw187 could fight far more effectively, while the Hs124 could strafe and bomb like the fighter-bomber version of the Bf110, but better, as it had an internal bomb bay, greater range by far (same with the Fw187 over the Bf110), and mount heavier fire power in its nose. As a night fighter it would be able to do better than the Do215 and have more stretch than the Bf110. It could do all the work of the Do215, Ju88C, and Bf110/Me210/Me410, and perhaps even what the Ju88G did later. Thoughts?
It might have been more compelling if Henschel had applied their experience in wooden aircraft construction into developing a similar aircraft. As it is, it looks like something in-between the Bf 110 and Do 17/215, though earlier and more sensible than the likes of the Fw 57. (it might have been worth trying the higher powered Bramo 323s on it as well)
Lack of an internal bomb bay would be unattractive and put it at less of an advantage compared to the Bf 110 (or at least potentially) but it might have had more appeal next to the Do 17, Do 215 and Ju 88, particularly with any conditions where resorting to carrying bombs externally would be necessary anyway. (and if wiki is accurate, the lack of bomb bay may have faciliated long range)
It seems like it might have been able to out-shine the Blenheim as a pre-war fast-bomber if nothing else, while also sporting impressive range.
Could it dive bomb as accurately as Me-410? Did it employ an armored cocoon around aircrew as Me-410 did? Remote control MG barbettes to protect rear? Could it match Me-410 internal fuel capacity of 2,420 liters?
These are the sort of details which separate an outstanding light bomber from a mediocre light bomber.
Much better to compare internal fuel capacity without auxiliary tanks.
Trouble is the HS 124 was a 1934 design. Cleaning it up might very well entail a new airfoil, new flaps, smaller wing, different construction,etc. The First HS 124 prototype flew before the first Whitley. The British might have been able to "cleanup" the Whitley but at what cost? How much would be changed.
A closer contemporary of the HS 124 was the Russian SB-2. The Russians tried to "clean it up" in a final version called the Arkhangelsky Ar-2 but it was replaced by the PE-2.
Henschel went on to design and build the HS 127, the Hs 128 research aircraft and the the HS 130 high altitude planes. They used little, if any, of the structure of the Hs 124 even if they did use knowledge gained in the construction of the Hs 124.
Clearly there is a miscommunication here, I'm not saying the Hs124 was literally the Me410 come early, rather its a bomber in a similar role, minus the schnell part of it. Its relative lack of speed, but increased manueverability is actually a boon for tactical bombing/ground attack, as is the STOL capability. Rather than going for top speed to avoid enemy aircraft as a tactical bomber it wouldn't really want to be too fast, instead it would want to be able to be more accurate with a linger ability that its range and maneuverability allow. With improved wings it can get faster as needed later, which is that hard to do given how Ju88 wings continually lengthened, especially with the Ju188 variant, which got a new tail and nose too, but kept the core design of the Ju88. Getting wings like the A-26 would definitely be possible and improve performance with better engines.