I am also considering an engineering manager and also Ops Manager to ensure CP can concentrate on flight ops - please let me know your thoughts on this - could outsource of course but concerned we might not get the right continuity.
I would strongly recommend both, an engineering manager and an ops manager.
Your airplanes will have to go to a CAMO. Still they make mistakes and if left unsupervised, can burn a lot of money even without having the intend to do so or can make you operate illegal. (mine has overlooked a change in the MM and would have let me fly with a non valid stby battery - I caught it...)
IŽm controlling what our CAMO does and for 2 airplane flying say, more than 300hrs/year, IŽd say it is sufficient work to have at least a part time guy doing it. The older your aircraft get, the more important it is. Also there can be a lot of guarantee claims whilst your airplane is covered under warranty. I had several claims turned down that were claimed by the mx/CAMO company, that were paid after I weighed in.
It also makes good sense if the person watches the SB/AD/Service letters and gives a summary to flight crews etc.
If your chief pilot is flying as much as the rest, then IŽd certainly would think about a person managing operations. If this needs to be a real manager or more or less a secretary is - IMO - a question of how your CP sees his duty and probably what software you use to manage the whole thing.
FPlanning and permits is a major pain in the butt these days and certainly something worth to source out, if not youŽd probably need 2 persons do the job (again depending on frequency of flight and how sudden they pop up)
I used to fly a Challenger 300 (AOC air taxi) and we employed a single guy for FP and permits, which was indeed cheaper than outsourcing the whole lot. (there was second small jet in that ops)
An indoor solution usually works better in terms of using the experiences made by the crews - I do my flight planning myself, but get the permits from a provider with 5 employees. And even at that small place they sometimes manage to forget what my special requests are...
I also hate to have to deal with a different person every time I call. But that is a personal taste thing...