I have actually just added a VOR route option to SimBrief’s route finder.
To generate a VOR route in SimBrief, first enter your departure, arrival, and aircraft type as usual. Then, scroll down to the “Route Finder” section, change the “Route Type” to “VOR ONLY”, and click “Find Route”. You can also include or exclude certain VORs by using the appropriate text fields on the right-hand side.
The VOR Route Finder isn’t quite perfect, but most areas with sufficient VOR stations seemed to work well during my testing.
If you want more VORs in your route, or if you want it to plan VORs which are closer together, simply lower the “Estimated Altitude” (for example, by default it might be set to something like 24000, try lowering it to 10000). The VOR reception distance depends on your cruising altitude, so lowering it should result in VORs which are closer together.
Let me know how it works for you!