The existing exploits in vesta are critical, vesta is dead. You’re right with additional costs, but usualy this is “just” a month. You would need to do anyway a full backup, doesnt matter how you want to try it.
Vesta can’t be migrated to hestia, a clean OS is a need to gain any support. You can ofc try out whatever you want, but you should also calculate risk and effor. Stay on vesta is probaly a bigger risk, due to it isnt maintaned anymore and has unpatched exploits. Compared to the effor and costs you need, a fresh installation on a separated vps is probaly the best way to go - at least in my point of view.