I haven’t played yet, but a minor IC in Romania could be useful for two reasons:
(i) Allows production (probably infantry) on the Southern end of the front, away from where the main German force is collecting and heading; and
(ii) Allows the production of sea units in SZ100. Building sea units in the Med is important for Germany for three reasons:
(a) can build a sub which will survive longer in the game than the Atlantic U-boats and can deny the UK one NO; and
(b) you can build a transport and get German men to Egypt, gaining a NO.
© You might also like to have the option of building ships to support the Italians if the US heads for the Med.
It might be an appropriate G2 or G3 purchase.