There’s two basic allied responses to holding France G1.Run away and allow Italy to clean up. Bulk up France with UK so Italy can’t take it.
In case (2), I say surrender, even though it may cost the allies the entire RAF. In case (1), you may be able to keep playing. I’ve got a game going now where Paris did fail, I think I should have deferred the DOW on USSR until G4 and played Japan as normal. This does allow a few allied actions like USA reaching the med or Norway. However, it is better than letting the Soviets push back all over the shop and get communism objectives for Scandinavia etc. I suppose this is a bigger deal in balanced mod because as soon as you DOW, you release the increased NOs for USSR. Also, all the money from being at war allowed the Soviets to buy enough planes to stop me from being able to effectively strat bomb Moscow.