Utrecht wasn't signed but Le Roi Soleil knew that trying to unite France and Spain was politically impossible, most assuredly by this point in the war if it had ever been a realistic prospect at any previous point, which it hadn't. I strongly suspect that in these circumstances Louis would feel the need to make a stipulation in his will on the successsion, which is not too implausible as he did it IOTL, upholding Utrecht, and going further than that in depriving Philip of Spain of the regency, which was also his by right of blood.
In short, I think you are going to get Berry as king. The only way you could realistically get Philip V as King would be if Berry and he did a swapsie of their kingdoms, as by the rough terms of earlier Spanish succession provisions, but that's too arty farty in a situation in which there would need to be an immediate political resolution.
In short, if you're trying to look for a way to shortcut to a Franco-Spanish union, political reality stands pretty firmly in the way of it by this point.