The utterly ideal situation for me would be to get in a head coach strictly on a two year contract, with Darren Moore being his assistant (one of two if the guy wants to bring one) with the approach that Darren is lined up to take over after that.
A lot of the really successful teams adopt a system of promoting internally through a system of progression and talent recognition. I wonder how Darren would handle a 3-4 game dip in form in November of such, especially if we've a lot of the team to replace.
Aim high for the next coach, bring in the very best person we can (which probably means aiming at an old head who will come for the money, Luiz Felipe Scolari for example). Pour as much knowledge and wisdom into Moore and the other internal coaches as possible and then promote from within.
Lets try thinking more than 1 year ahead. Lets put a proper system in place!
This is muddled thinking. For a start, what coach with any confidence in his own ability is going to take a job where he is just keeping the seat warm for someone else? I doubt if such a person exists.
But just for a moment, let's assume that we found this mythical person and project forward with a couple of very plausible outcomes.
1 He gets us promoted in his first season, and gets a top ten finish in his second, making some excellent signings along the way. The team is playing with confidence and there is a feel good factor about the club. What are you going to do? Sack him and replace him with Big Dave? I don't think so.
2 He is a disaster and we are bottom of the Championship with half the matches played. What are you going to do? Sack him and appoint Big Dave 18 months ahead of schedule? Sack him and look for someone else to appoint in mid season for 18 months? What if this person then steers us clear of relegation and then gets us promoted in the second season? Sack him and replace him with Big Dave? I don't think so.
We all love Big Dave. He is a legend. But maybe he needs a bit more experience to undertake the role of head coach. In which case, we appoint the best person we can find, and offer Big Dave a role within the new set up. If he continues to develop as a coach over the next few years, we can look at him in a few years and make the decision then. On the other hand, if he is ready now, let's appoint him now. This is a decision for those with a finger on the pulse within the club and they have to make a judgement. But, I would suggest, your "utterly ideal situation" is not an outcome that has even a sniff of actually happening.