The Fw 190 was built because of the radial engine. It would have shared the same fate as the He100 if it took engines away from the Messerschmitt.
Even a poor performing He 100 dragged down with armour and cannon would still have been one of the fastest machines of its day and superior to the P-40 and 109E. The question...is whether in a 1944 timeframe would a 109 be better than a 100? A silly question to ask in 1940 but I suppose that is what its about.
That's also part of my point: with proper strategic planning/logistics management, etc, Messerschmitt would NOT have gotten priority for engines like they historically did, and the Bf 109 should have been replaced by something better following the E/T models ... or at least they should have been trying very hard to stop production in favor of something more potent as both a defensive and offensive weapon. (if DB-601N/E/605 powered He 100 and Fw 190 derivatives proved genuinely worse than the existing 109F/G series -not just in speed/climb, but firepower, range, visibility, dive performance, and handling -on the ground and air- then they'd have been still stuck with the 109, but I see that as rather unlikely -there's the Fw 187 to consider as well, especially as a defensive weapon)
That said, with RLM policy as it was, using the Jumo 211 for testing on more fighters might have helped too. (particularly engineering a plane flexible enough to adapt to a variety of power plans and potentially directly switch between fairly similar engines on the production line -like say, designing the He 100 a bit less tightly and allowing it to accept either a Jumo 211 or DB 600, though the Fw 190 would probably be easier to adapt to such, perhaps somewhat like the differences between the Merlin and Allison powered P-40s) Though in heinkel's case, designing a fighter that expressly shared at least partial parts commonality with the nacelles and radiators designed for the DB-600/601 and 211 powered He 111 models would have been efficient/attractive in terms of mass production and maintenance.
And on the note of the Fw 187, here's some relevant photos of the retractable radiators used on the single-seat prototypes:
http://www.warbirdphotographs.com/LCBW6/FW187-V2-16f.jpg
http://www.airwar.ru/image/idop/fww2/fw187/fw187-5.jpg
http://www.airwar.ru/image/idop/fww2/fw187/fw187-6.jpg
http://aviarmor.net/aww2/_photo_aircraft/f_ger/fw187/fw187v1_1.jpg
http://aviarmor.net/aww2/_photo_aircraft/f_ger/fw187/fw187v1_2.jpg
(all rather like smaller versions of what the He 111 used)
And also the radiator from the DB-601 powered V5 prototype with radiator in fully retracted position on the ground:
http://s412.photobucket.com/user/ruspren/media/ruspren001/IMG_0695_zps8b3c015f.jpg.html
Those DB-601s apparently used a similar steam/evaporative pressurized cooling system as well, so not the standard DB-601A/N models used on contemporary 109Es. (also not like the surface cooling used on the earlier DB-600 powered Fw 187 prototype example)
Much of this was discussed at length here:
http://www.ww2aircraft.net/forum/aviation/fw-187-german-51-a-38757-20.html
(albeit with a fair amount of cross-talk and missed points along the way, the more recent post I made there attempted to summarize some of that information and address some of the confusion)
The cooling system in the all built versions of the He-100 used evaporative, ie condensing steam in the wings, for cooling. The tiny retractable radiator was added between the wing header tank circuit, and offered negligible cooling when retracted.
We know that the last production block (D-1) used this system as photos of the engine bay exist that show several features related to the steam cooling system.
This is all true except for the surface cooling aspect. All versions used pressurized steam cooling systems, but only some of them used surface cooling (both for condensing and -more so, I believe- simply cooling the hot, pressurized liquid coolant) as well as surface cooling for oil in the rear fuselage. (non-evaporative in this case)
Such a system can just as well apply for using a fixed, centralized radiator for cooling/condensing the water and oil before sending them back to their respective header tanks, and this is what the D-1 supposedly did (as well as the prototype modified to test this arrangement). It should also be fairly similar to the pressurized cooling systems used on the DB-601E and Jumo 211E (and later models) including use of a steam separator on all models. (I'll need to check again, but from what I recall, all those systems took advantage of limited boiling inside the cooling jacket, nucleating mostly around hot spots in the engine, and the water was then sent though a centrifugal steam separator, sending the liquid portion straight to the radiator -and/or surface cooling ducts- while allowing the limited amount of water vapor to condense before joining the rest of the liquid)
I believe in the above drawing the items labeled 2 are fuel tanks, the items labeled 1 are part of the cooling system. Not sure on item 2. Areas on rear fuselage, fin and horizontal stabilizers are part of the oil cooling system.
Some of the late series aircraft got a fuel tank added behind the cockpit.
Indeed, and the portion labeled 3 may be the oil header tank or just an expanded portion of the oil cooling system with the rear fuselage being insufficient? (I recall that being mentioned as well)
The issue with the wing fuel tanks and self sealing is the shape. Large area but flat tanks require a greater weight of self sealing material for their capacity that squaty fat tanks. And the loss of capacity is proportionally greater when the hight is fixed ( wing thickness).
Indeed, though allowing the areas relegated to surface cooling be filled with fuel tanks (as with the P-38's intercoolers) this difference could at least be partially offset, in spite of the difficulties of flat fuel tanks.
One thing I missed on previous discussions on the P-39's wing tanks was that the XP-39 had lacked any provision for guns in the wings and could thus rely on the outer wing panels for fuel where the production models carried the 4 M1919s and 1000 round capacity ammunition boxes. (the higher weight to volume ratio for the P-39's tanks compared to the P-40's would still be relevant, of course -flat tanks are heavier than tub tanks of the same volume) In fact, if the He 100 was anywhere near (or better than) the drag characteristics of the P-39, it would have been a winner, over the 109 at least. (powered by engines on the level of the 109F and G ... hell, even the contemporary Jumo 211 models would be better than what the engines the P-39 was getting throughout the war, same for the sluggish WEP ratings -at least compared to British practice)