[A class 1 medical is a professional pilot's medical; I'm assuming you mean you can't get a class 2 medical.]
The medical requirements will change - the equivalent to the NPPL medical will be the Light Aircraft Pilot's Licence medical, the details of which have yet to be published. If you have an LAPL medical, you can only hold an LAPL licence, not a PPL - the LAPL being the equivalent of an NPPL.
It will be feasible to parlay a BGA glider pilot's licence into an EASA LAPL(aeroplanes). You can get the BGA licence & use that to get an NPPL SLMG & then SSEA, or you can convert the BGA licence into an EASA LAPL(s) and add ratings to your licence through the EASA system.
The licenced airfield requirement no longer applies. Be aware that a BGA motorglider instructor cannot instruct for an NPPL, you will need an actual NPPL SLMG instructor.
We don't yet know what the conversion requirements from the BGA/NPPL system to the EASA system will be. An optimist would say that if the BGA/NPPL syllabus is equal to or exceeds an EASA syllabus, then the equivalent EASA licence & rating will be granted.