If the flight plan isd accepted by the IFPS then the route and the level are acceptable to ATC.
That is whole reason for having the IFPS in the first place.
If ATC do not want FL70 used on that route they need to tell the IFPS or at least put a zero rate flow restriction at that level.
Otherwise, it is a waste of time having the whole IFPS and CFMU operation if local controllers can set their own personal agenda.
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I have once this past year come across a similar situation in the UK - IFPS accpets route, no CTOT but we have an extended delay because London ATC do not like our route. The result was that the company had to ring the IFPS supervisor who had to ring the local supervisor who rang the controller who then suddenly cleared us. It was not a level issue but a routing issue but the primciple is the same.
Regards,
DFC