Hi Vernand,
I've just had my initial class 1 issued with an OML restriction in the UK. As far as I am aware the UK CAA is the only EASA member state who will issue you a Class 1 initial with an OML restriction. Each case has to be assessed by the CAA if you require an OML. My advice would be to come to the UK (before Brexit!) and get your EASA class 1 issued here with the OML. Then apply for a change of state of medical issue to which ever country you will be doing your training in. I know my flight school required your EASA class1 to be issued by the UK CAA.
Good luck!