I like questions of the day...
1) Is there anything to be gained by having "reactions" enabled when playing in the strictly turn-based mode? It seems to me that only the AI is capable of using this effectively.
Reaction movement does work for the Player but it would seem to be best used for an army that does not have move orders. I think that if you move an Army that has a Reaction order you stand the risk of moving it away from its trigger provinces before the enemy forces arrive to trigger the reaction movement. You also need to decide how big the reacting force is going to be and have only a limited time to make that decision. During August and September turns in the West, reaction movement for the French Fifth Army and the BEF can help block the German left wing if the AI is aggressively prosecuting the von Moltke Plan. On the other hand, any reaction movement can leave the reacting forces isolated and vulnerable and at the mercy of battles fought in nearby provinces and can also see you fighting outnumbered and at a disadvantage. Like most WW1G decisions, there is no absolute "right" response and everything is a trade-off. Setting Reaction Movement can be a powerful operational tool or the recipe for a disaster of significant proportions.
2) Playing as the Entente, I can't see that there is anything to be gained from Romania joining the war. They have only one army, it is weak and scattered everywhere. What is more, it destabilizes the Southern tip of the Russian front. So very annoying!
The chances of Romania eventually joining the war are considerable and if it joins on the side of the Central Powers, Russia's problems increase if only because the defendable front becomes about eight or nine provinces longer with the existing force levels to take up the slack. Getting Romania on your side (as the Entente) provides an opportunity to outflank Austria's Galician Front and spread the Austrian army out, thus reducing its offensive potential. Remember, the longer the war drags out the more it tends to favour the Entente and attacking is necessary in order to win. Even if you choose not to use the not inconsiderable Romanian Army in an offensive war, it holds the Russian southern flank relatively solidly.
-C