Likeness approvals almost never hold a figure up. In the last three years I can only think of one. Ripley. Batman returns was a design and engineering and overall look issue. Drax was due to tech issues that caused the scarification to not translate and needed redone. Prime is engineering issues. Yellow jacket the same. The xmen first class and DOFP wasn't held up, it was that they didn't get the licensing from the actors at all.
And figures are mostly on time after they go up for order. Out of the last 100 figures I only found a few that where late or delayed. Not the "sideshow" delay that people call delayed but almost never is. A delay in hot toys release schedule. Those are all that count in regards to production times and approvals, and you said approvals.
It's just not a really problem. Only very few times is it a likeness approval. It's more often an engineering and overall appearance issue. Everything is required to be approved. The entire process is what takes time. Having a head sculpt isn't going to significantly increase production time. If at all.