This is your solution - make your pool for pppoe sessions be the /25 from the provider, and skip the first address in that range when defining the pool.
i.e. x.x.x.2-x.x.x.126 or x.x.x.130-x.x.x.254 and use x.x.x.1 or x.x.x.129 as the “local IP” in the profile.