I used the Nano pass framework for my language when I was in grad school and loved it. I forget the exact count but I think we had 40 or 50 passes. Generally each pass either did some analysis that would be consumed by a later pass or it rewrote some higher level concept or feature in terms of more primitive operations.

Nanopass had a DSL for describing what forms you delete from each intermediate language and which forms you add. Each pass was generally pretty small then, usually just replacing one form with some set of other forms.

Be cause each pass was really small it was pretty easy to reorder them. Sometimes we figured out if we moved one optimization sooner then later passes worked better. Or we realized some analysis was useful somewhere else so we rearranged the passes again. The pass ordering made it really clear which analysis results are valid at each point in the compilation process.