Obvious ridge in matte black metal roof

We just began the install of our matte black metal roof. It’s an older house and the roof deck, although in good shape, had some variation. We didn’t realize how much it would show up. Now wondering if some sort of furring or backer rod would help? Picture attached.

Purlins and battens would help level up the roof here but nothing is going to help what you have going on now.

That's the only section that is on so far and our roofer said he's happy to remove it, just trying to avoid the same thing elsewhere on the roof. Expecting some big dips as the house was built in the 40s and has been added onto, but looking to avoid this type of harsh ridge.

If they are happy to remove it, have them install battens/purlins and if that is an insulated roof an in a hotter climate, some cross battens will allow for some above deck roof ventilation.

The house is also still completely open from inside. No drywall is up yet, it’s a gut/remodel. Behind schedule of course so was hoping we didn’t have to redo the whole roof deck as the ice and water shield is on. Can battens be installed over that? Or is there a way to take advantage of the fact that there is no drywall up yet and fix it from inside?

No way to fix that from the interior. Roof needs to come off.

Not sure if my last post went through, so, sorry if duplicative. Can battens be installed over the water and ice membrane? Would prefer not to tear that up too, but it doesn't seem like something we should be putting holes in. It was installed directly onto the roof deck, old shingles were ripped off. Additionally, we still have access to the roof from inside the house as it was a total gut and there is no drywall up yet. Any chance there is an easier solution that can be done from inside?

Yes it can.

I would still want some underlayment over the battens after that for a drainage surface.

Thank you for your help!