The issue I found with this approach is that the other big reason to use VaultWarden is for multi-user support. However, then each of your users need the same VPN setup, which can be hard to manage if you support a non-techie or Luddite.
Exposing it to the internet isnt safe, but it’s more accessible then setting up VPNs for everyone with proper routing and stuff. The actual Bitwarden service isn’t that expensive last time I checked, and I think it’s probably the best, simplest solution if you need to support multiple technophobes.