PvP rank will not matter THAT much in frontlines, compared to the current PvP.
In fact, they even announced they are revising PvP such that everyone get access to the PvP skills from start and that the Morale stat wouldn't have any effect in Frontlines.
So the only advantage you can get from higher rank, therefore more PvP points, is somewhat boosted PvP skills compared to the base.
That is in addition to iLevel syncing to 80 (uncertain if that is only from above 80, or if it's syncing up to 80 from below as well).
All this to ensure that even people new to PvP can enjoy Frontlines without being instantly killed by people with much higher ranks.
We also don't know how hard it will be to rank up with Frontlines compared to current. And Frontlines PvP points is in addition to tomes.