So providing you do not write anything indiscrete to those locations that have a different use of the bits, you should be fine.

Dual Data Pointer Registers: To facilitate accessing both internal and external data memory, two banks of 16-bit Data Pointer Registers are provided: DP0 at SFR address ocations 82H-83H and DP1 at 84H-85H. Bit DPS = 0 in SFR AUXR1 selects DP0 and DPS = 1 selects DP1. The user should ALWAYS initialize the DPS bit to the appropriate value before accessing the respective Data Pointer Register.