Isn't that what the FMS is made for ?
Not provide precise glidepath guidance/reference down a build-your-own approach, no.
Our box (Honeywell, but not Scarebus) allows you to create a "runway" at any location/coordinates, and from there the normal 3° slope will be projected back. That would be the most accurate way of doing it. VRs, because you can only get them to within 50ft, aren't going to help when it counts IMO.