Fatigue is the only thing to guard against imo. Rafa needs 3 things to be amongst the favourites at any tournament, on any surface: happy, confident, and well. He seems so happy right now. Confidence you get from winning recent matches. Wellness is a combination of feeling fresh and injury-free.
From what Rafa tells us, the recent foot problems came as a result of inactivity during COVID. So he needs to keep moving.
Even at 36, and Rafa is by no means a typical 36, 12 tournaments a year is not over-playing.
Your worry is that these tournaments are concentrated in bursts, like the clay court season? Clay is the easiest surface on the lower limbs. Furthermore, if it goes to plan, winning lots of matches on the clay leading up to Roland Garros means that Rafa is at peak fitness and brim full of confidence at the start of the FO. Often overlooked, it also means that his closest rivals are demoralised. If no one could put a dent in him at BO3, what chance do they have in a BO5?
I think and hope he will play Madrid, only if he has an easy Barcelona (wins easily or loses early) but if it's a tough week he will save himself for Rome.