This discussion has been going on for a long time indeed, not restricted to EASA.
Correct me if I am wrong but doesn't the UK ANO already prohibit a flight crew member to be paid for his services with a non UK licence in Section 1 Part 6?
Deeming a non-United Kingdom flight crew licence valid
(1) Subject to paragraphs (3) and (4), paragraph (2) applies to any licence which authorises
the holder to act as a member of the flight crew of an aircraft and is granted:
(a) under the law of a Contracting State other than the United Kingdom but which is
not a JAA licence; or
(b) under the law of a relevant overseas territory.
(2) Subject to paragraph (4), for the purposes of this Part, such a licence is, unless the
CAA gives a direction to the contrary, deemed to be a licence rendered valid under
this Order.
(3) Paragraph (2) does not apply to such a licence if it authorises the holder to act as a
student pilot only.
(4) A licence deemed valid under paragraph (2) does not entitle the holder:
(a) to act as a member of the flight crew of any aircraft flying for the purpose of
commercial air transport, public transport or aerial work or on any flight for which
the holder receives remuneration for services as a member of the flight crew; or
(b) in the case of a pilot's licence, to act as pilot of any aircraft flying in controlled
airspace in circumstances requiring compliance with the Instrument Flight Rules
or to give any instruction in flying.
(5) A JAA licence is, unless the CAA gives a direction to the contrary, a licence rendered
valid under this Order.
Anyone?