Learning from other sectors pays off!
We construct things as long as history goes. We build bridges, roads, undergrounds, malls, etc. etc. And at every construction site, you always see a construction cabin ("directiekeet"). Out of luxury? Of course not!
It is simply a necessity to oversee and control all aspects of the construction at hand and in the midst of where the action takes place. And with the long history of complex constructions in mind, you might treat this as a learning point.
It is amazing to see that even today when so much depend on useful, stable and solid IT solutions there are still many projects (like constructions) being deployed without a proper project management governance in place, the equivalent of a construction cabin. Is it a matter of just being "forgotten" or unawareness of its importance? Or has it to do with controlling costs? Whatever the reason there should never be a discussion about creating a solid governance on contractual agreements, quality, project milestones and planning, resources, costs and risks. Usually, all those aspects requiring attention cannot be covered by just a Project Manager. In my view it will be inevitable in most cases to include additional staff to create a proper governance structure. Setting up a proper "construction cabin" may never become an adjustment variable!
I have witnessed many projects where line management eventually got so heavily involved that it was not anymore to oversee its progress but interfering with all aspects of the project management. Although, I would never exclude the authority of line management to challenge the project management office and take decisions based on changing risk profiles or unforeseen changes. But it is devastating if projects are being (micro-)managed by line management from a distance, unstructured and with insufficient knowledge and empathy. Mostly, this has to do with either a relentless focus on cost or a lack of trust in the current governance structure.
Concerning cost, how often do you hear (mostly after the fact), penny wise pound foolish? In normal circumstances the cost of governance is always calculated as part of the project. But in case it is insufficient and the project needs more coverage, than I would strongly advise to avoid getting involvement by more line management. Instead accept the cost of more governance within the project. In the cases I have overseen, ultimately the return will always be in your favour.
Concerning lack of trust. If that is what the opinion is of line management, than why not act and replace? This is also an appeal to each participant of the governance structure. Never continue in a distrustful relationship. In the end you will always be at the short end of the stick. Trust can not be switched on and off.
The setup of a proper governance structure is without a doubt a must within every project. Of course, its size will depend on the complexity and size of the project or program, but it can never be omitted.
Will you ever witness a project without a proper structure in place, than ask the question, what is so different compared to the construction world where every assignment has at least one construction cabin...
As long as IT cannot demonstrate an unblemished track record...