Managing a larger roster/program - Advice wanted

I dont know so much about the youth level stuff, but in regards to a larger hs i have been there many times.

I imagine many, if not most, of that 150 will be on your frosh team. Which, during the season you will not have as much day-to-day oversite over. So that being written, you need to get a GOOD guy at the top of the frosh team. Someone who you trust to work with the kids, but also be rock solid with admin and parents.

Outline everything for that program off the start, go over it with those coaches and make sure they are bought it. And im not even talking about techniques and schemes as much as running the program day to day. Make sure they are capable of handling a frosh team of 100+ and have an idea on how to organize practices and get kids playing time.

I imagine your previous experience has already prepped you on what needs to be done with the v/jv stuff. But that massive frosh team that is separate from you most of the time can be a monster. Invest wisely in it early on, so it isnt a pain for you during the season

This is huge.  At multiple schools, our best years have always been when we had a very reliable lower level head coach.  We've done it a few different ways - basically deciding whether to have JV practice with the freshmen, the varsity, or jump between the two.

Conversely, we've had years where the freshmen "head coach" is also tied up with varsity stuff or just not super committed to the lower level role, and that doesn't work well.  There has to be somebody "in charge" for it to work well, in my experience.

I was at a program with 130 players 9-12. Can't really help with the lower levels. They already had staffs for the middle school and we just left them in place.

At the HS level, we were 100% 2 platoon. Everyone warmed up and went through Indy & ST together. After that, freshmen went to a separate field. We did inside run, 7 on 7 and team separately. After team, the freshmen would come back over and we would end the practice together.

Freshman usually had between 4-6 coaches. Usually a combo of former players, young motivated guys and old vets that enjoyed coaching, but no longer wanted to put in as much time as the varsity staff.

We don't have quite that many but close.  We divide them up between 2 groups- those that will/have a chance to play on Fridays and those that won't.  We have them on 2 separate but nearby fields.  We don't have a dedicated Frosh HC, but do have a defacto one.  All of the coaches rotate between the 2 groups save a couple.  The HC, Coordinators and the QB coach are always with the varsity group.  Every other position coach will spend at least 1 day in its entirety with the younger group.  That way everybody gets coach by the varsity coaches.  The HC will occasionally slip over to the young guns field from time to time.  

I'll get back to you on that - I'm helping a buddy put things together and there's still a bit to figure out. At our prior school we had about 10 paid (peanuts) plus 4-5 volunteers. At new stop I'd imagine we're in a better spot but I'll update you. May also ask if there are any potential pitfalls to look out for with a significantly more talented roster. Over the past 5-6 years we've had about 75% of our roster train D and O out of necessity so it's a big change for us.