Firstly moving to 1 nap you HAVE to leave to him, if you force it you will have a cranky baby, my ds#1 didn't go to 1 nap/day until 21 months Yes 21 months.
Honestly in my opinion, you don't need a plan, once they get to this age (being solids starting to be equal to milk in importance) I think you work towards what works for you... EVERY BABY & FAMILY is different.
You could start dropping one of the day nursings & offering a snack first & it you think your lo is ready then you can offer solids before the nursing in the am too. As long as he is getting 3-4 milk feeds at 9months that is what is "recommended". Then by 10 you could drop to 3 & if you stop bf before 12mo then you really need to offer formula instead. I assume you are wanting to wean due to returning to work... but that would mean you could stil bf at some time of the day.
Like I said, you need to work with what YOU & JENCY need & not to a plan.