Hello!
I would like to help you with this task.
About my experience: I have big experience with network administration (VLAN, SNAT, DNAT, iptables, iproute2, multiWAN, tcpdump...). Big experience with OpenVPN servers/clients. Serial connection 2,3 servers for more security. OpenVPN over IPv6 and other.... Experience with VMWare ESXi, MS Hyper-V, Proxmox VE, Mikrotik, Ubiquiti and some different skills.
As real example I did similar project where I have about 180 VMs, 1 intermediate OpenVPN server on linux and 180 end VPSes for each machine. All 180 OpenVPN clients work on intermediate OpenVPN server. So for each machine I use separate routing tables, and in this table default route via each end VPS. Also I add routes via route-up scrips. If you want to be sure in my competence I can show you it.
My other skills and reviews you can see in my profile.
Я так же говорю по русски, возможно это будет плюсом.
Hope for cooperation!
Thank you!