Much has been said about "getting the right people in the right seat", by business writers such as Jim Collins (Good to Great) and Gino Wickman (Traction). An important part of that message is the need to carefully craft the "right seat".
In this context, the "seat" is a specific position, and it carries a title and a mandate or job description. Mandates may be implicit, without a written version. In many cases, duties are explained during recruitment and selection, with new employees simply given a title and home department. Position details are explained by the supervisor during orientation and training. This is quite appropriate for many entry-level positions, but much less so for supervisory or management jobs.
The best approach for supervisory and management positions is to design the position for the company, including setting out an explicit mandate, and then find the best person for that position. Designing mid-level positions around people subordinates business performance to employee preferences.
In reality, positions are often designed or re-designed with a specific person in mind, because of skill shortages or personal allegiance to employees. As a business owner, you should acknowledge that this represents a compromise between what is best for the company and what is preferred by the employee. If you don't explicitly consider and assess this compromise, your company's performance will be limited by the interests and other limitations of its current employees.
I suggest you start from the idealized perspective of what the business needs, ignoring for now who might or might not be a good candidate. Set out the specific roles for the position in question. There are generally three components; responsibilities, authorities, and accountabilities.
Responsibilities are the actual duties to be performed on an ongoing basis, including supervisory functions.
Authorities are the specific types of decisions that are authorized for the position. Think about what you expect the person in the position to deal with on their own, such as subordinate hiring, compensation, review, discipline, and termination. Does the position need a certain level of authority make purchasing or pricing decisions? What decisions do you need the position to make, without going to its immediate supervisor?
Accountabilities consist of two components. Firstly, there are those specific results the position is expected to achieve, such as sales targets or other Key Performance Indicators. Secondly, there is an explicit statement of what other position (not person) in the company this position reports to. Where does this position fit in the company structure?
Set all of this out in a brief mandate statement for the position. This is what the position would be, given that you had the perfect candidate for that "seat". Now, look at who you have available or in mind for the position, and assess the match between them and the position. If you must compromise, then at least you will be doing so with explicit knowledge of any shortfalls. You may be able to make up the deficiencies elsewhere by explicitly assigning parts of the mandate to other positions. At the very least, knowing the person's shortfalls in the position will allow you to work toward remedying these.
When you are just starting out, all the roles in your company are fulfilled by the founder(s). As your company grows, you will gradually divide up the work into component roles, while still having situations where one person's overall job consists of several positions. Give each role a specific mandate, including accountability to another specific position.
People fulfilling multiple roles can have multiple bosses, provided there is only one boss for each role.
Resist having multiple persons sharing the same supervisory role (i.e., teams responsible for jointly managing one or more positions). When you feel a position should report to a team, resist that temptation and instead link the position to a single position within the supervisory team. The rest of the team then becomes advisory to the named position within the team. Remember, committee accountability too often means no accountability.
Having explicit mandates for each mid-level position helps everyone keep decision-making and management accountability straight. Better company performance will result.