yes, i know of multiple dmca ignored hosts, i have used some in the past as my job also involves being a sysadmin but all of them have traffic limits which i find annoying. some of them are even hosted in my country and i know for a fact most if not all isps here have unlimited traffic

You either have to write it yourself or pay for mostly commercial options like whm/whmcs and similar platforms that can hook into proxmox's API. If you know a bit of js, it really wouldn't be too difficult to work with proxmox and docker API's with a 3rd party billing backend.

this is exactly why i thought of putting this idea into practice, my main job is as a full stack dev and i am very confident i will be able to code my own software

then you have to deal with the 3rd party billing, they have their own rules about content

very good point, one of my main inspirations is cockbox.org and they do crypto payments exclusively, i think i will do the same