Have you considered processing the original recordings using AI? I've witnessed some truly amazing results. I've had twenty year old Skype call recordings sound like we were sitting in a recording studio.
Yes, that's exactly what we did here. We fed the originals to AI, but we did give it wiggle room to make a cover version and not follow the original exactly. I think I will play around with running a few tracks through and telling it to follow as close as possible to the original and see how it sounds!
Depends on if you're willing to pay or not. You can do it alright locally with DeepFilterNet but honestly the best quality comes from Adobe Podcast's AI Enhance function.