Slippers, to answer your question:-
Q. "Is it possible / has anyone tried running two tactical positions with one planner? "
A. NO - A sector (or bandboxed group) consists of 3 staff - Tactical, Planner, Assistant - I believe this is an SRG requirement, unless anyone out there can put me right ? - All 3 staff must be present for the sector to open LEGALLY. What you are suggesting requires 2T,2P,2A (at least until all the A's are made redundant that is).