Scope of architectural service due to own work

Drywall, tiling, flooring, painting, preliminary electrical work, drywall, etc.)

I am just realizing: except for drywall and electrical work, you also have to do the rest yourself as a subcontractor with the general contractor. Many still take drywall and the preliminary electrical work additionally as subcontractors. In that respect, there's not much difference. However, I would only recommend drywall, including roof insulation, to my worst enemy to do it yourself.

I would only advise my worst enemy to do drywalling, including roof insulation, by themselves.

Especially the kind of drywalling that is often used as a substitute for detailed plans ;-)

I have professional experience in the field of construction law myself, and the responsible caseworker sits with me in the office. Therefore, I think I can handle the construction law part myself.

Doesn’t sound like you have building plan approval authorization. So your role will be limited to mail delivery and inquiries or pushing things along through informal channels. You should also know that not just one caseworker but several departments have to give their approval. You will be, just like all other builders, nicely slowed down.