Unfortunalty this does not work as well. The SPA event triggers still one day later. I guess that is because the nation is new then.
I wouldn't change the intervention events to fire immediately, on the contrary I would make them historical, which AFAIK are later than happens in the game. For this to work, you would need to make somehow the republican AI versus nationalist AI as passive as possible until the major interventions fire. However, don't bother if it isn't easy to achieve, as it is not as important as other aspects.