Having re-read the NPA the process imagined seems reasonably straightforward.
- you file a Y flight plan with the VFR transition before the IAF
- The Y Transition tells ATC you will not be making an instrument approach
- This is normal practice in countries that do not allow IFR flight plans into VFR only airports
- I would expect ATC to descend you on track to your destination down to MVA. As a note, the NPA currently says Minimum Sector Altitude and my view is it should be the least of Min Sector, Min Safe, Min Vectoring altitude
- At this point you are either visual with the surface in VMC and land, or not and 'miss' getting a climb and heading to your alternate or a hold to think/wait for better weather
This is how most light GA IFR flights recover in the UK (as most airports don't have instrument approaches). I fly IFR all the time out of Fairoaks and have had to hold once for a cell to go through and divert once. But most of the time the weather is good enough to get visual at or above the MVA.
PS - crossed with BW
With regard to departing 'not IFR' and picking up your clearance on the way... if only I was based at Cambridge or Oxford rather than Guildford ..... better universities AND Airports with approach control! Sadly all my IFR Departures are 'head west young man and ROCAS while we try and get you a join'