I run 42mm tires on A23 and it works quite well. A wider rim would do two things, one is make the tire effectively wider, the other is to allow lower pressures to be run without the tire rolling on the rim in hard corners. For me, that happens at about 25psi under my 220 lb, so not much of an issue.

On a racing bike, theory has it that a wider rim with a wider tire forms a smoother teerdrop shape. But if you just want something that works, it is almost a non issue.