reverse print onto clear.
dependent on how much cover of print you may need to print a hair-line to show the border of the artwork.
then laminate in white vinyl.
trim up the graphic over a light box/table as this will show up the hair-line for trimming/finishing much easier..
this will reduce the amount of on-site work and should give the best finish as a result.
i guess it depends on how many you are doing and if the prints go right to the edge of the window, then precise trimming isnt required because you will be butting the vinyl to the edge of the glass anyway, then triming.
if there is only one or two and you are confident enough with your application skills. then applying to the glass and flood coating the rear then trimming would be quick done too.
uv printing a board would be the quickest and most cost effective for you, that’s assuming your printing in-house, but i think it depends on the finish your customer is after as you said he is stipulating high quality interior fitting, and then how you intend fixing it to the glass.
if you do have a UV Printer and it has a white ink option. you could reverse print onto clear vinyl and back it with white?
its difficult without seeing the job in question…