Why wouldn't they create the He-112 first - the Hurricane equivalent; and then the He-100? The latter would take more time for refinement, but have a higher potential than the He-112. Have the FW-190 coming down the pipeline. The He-112 becomes the international sales piece in this layout.
I agree that He 100 (or it's ATL equivalent) would've been a good idea, especially since the He 112 will not be as performer as it was the He 100. Quirks are timing and production. Even with single 1-engined type in production 1937-mid 1941, Jagdwaffe was receiving far less fighters than RAF received Hurricanes + Spitfires (this obviously does not include what was bought in the USA, plus what French and later Soviets were producing). Thus re-tooling production lines for a new fighter in 1938/39 and re-training the workforce is bound to leave them with even less fighters in 1939-40, that combined with lower performance of the He 112 vs OTL Bf 109 will play havoc with LW plans, succeses and losses.
The He 112 will not become the international sales piece with advent of Fw 190 and He 100 - nobody will want the 3rd best German fighter. Granted, once all of the production lines are running smooth, the numbers produced will start improving, especially since the He 100 was allegedly far better suited to the mass production than the He 112, using much less panels and rivets.
What might be interesting is the He 112 with thin wings, not unlike what Tempest was to the Typhoon. Much less hussle on the production lines than wholesale change of type produced.
I believe the RLM original preference was for a limited number of basic designs, but they adapted (for good or bad) to cranking out multiple designs, prototypes, and production planes for a variety of purposes.
Choosing a limited number of basic designs was a sound policy, provided one's technology is up to the task, and there is no bias (political or similar) when making the choices.
Taking on 3-4 big enemies in almost same time was not a sound policy, but again that was not the guilt of RLM.