After 40 years in Spain, you should not be thinking the way you are. You can use a plastic A4 sleeve. I still have my paper driving licence in a sleeve. I refuse to change and even if did change it. My signature does not fit in the space that is allocated for, in the signature box of the application form.
Incidentally, can you please advise your experience to the UK authorities as they are hell bent on introducing a card in UK.