I think Valhalla, despite its relatively poor performance compared to ORS/OSRM, would be a nice addition to Vroom's routing providers. It's really unique in terms of run-time weights & costs, no other router can match that, except for BRouter. Anyways, with Mapbox ending OSRM support in a few weeks time and fully concentrating on Valhalla, it might also be a step towards future.

Of course it's possible to add Valhalla already via custom matrices.

Actually I think I'd like to tackle this myself, if no one else jumps for it in the next weeks. Recently started some C++ dev and this seems rather easy.