RNAV initial offset onto ILS

[FlightPathOBN]

ok ...(I removed the comment)

as noted, the timeframe for the system (the 30 or so seconds) made it difficult from a human factors perspective, and others (especially the RNAV purists) to set the waypoints, etc

In the US, there is the 8260.54A which specifies criteria for obstacle clearance evaluation of area navigation (RNAV) approach procedures; e.g., Localizer Performance with Vertical Guidance (LPV), Lateral Navigation (LNAV), Lateral Navigation/Vertical Navigation (LNAV/VNAV), and Localizer Performance (LP).
These criteria support adding an instrument landing system (ILS) line of minimums to an RNAV (GPS) approach procedure using LPV construction criteria at runways served by instrument landing system.

This may be of some help in the criteria and calculations behind this. ( I am not sure where .54 is with its use in the US)

In appears that the military has been using the RNAV to ILS for some time...