Private companies valuation - “optimal” capital structure

Hey guys, that’s my first post - hope this question hasn’t ben raised & solved already in other topics, in case just let me know which one.

Context: WACC calculation for the valuation of a private company.

As I understood from multiple trainings, videos and books, for the % weight of market value of debt and equity it is commonly used the mean or average of public comps’ related capital structure.

However, this “choice” relies on 2 “big” assumptions:

1) The public comps’ are closed to have the REAL optimal capital structure

2) The target private company will tend in the short term to the optimal capital structure as defined here above

But these assumptions may have some flaws, here some thoughts:

1) What happens if the comps in your peer group have completely different capital structures and no pattern emerges? In this scenario the average or mean figure is not really insightful

2) What happens if we don’t have control over changing the target company capital structure (e.g., valuing a non controlling investment)? In this scenario I think it’s not quite accurate to assume a different capital structure than the target company’s current one

3) What happens instead if we find the “optimal” capital structure based on public comps but then we notice that is completely different from the target company current one? (e.g., optimal 40% equity 60% debt and current 100% equity 0% debt)

Just to summarize I wanted to ask you whether in practice it is common to blindly follow the rule of averaging the public comps figures or if it ever happened to you to make some (big) assumptions based on the specific context (and if you can provide me some brief example of the situation).

Thanks in advance guys!

Emanuele