I'm having a bit ao difficulty picturing what your describing.
A picture (schematic) is worth two thousand words (I'm double dense)
I know I can do it with a relay (actually two of them as I want the inactivated side to remain steady state/on) but this would put them out of phase with the rear & dash.
I could install the relay(s) so both the front & rear lights are in the switched relay cuircit so that would eliminate one of the above concerns.
I would have to find a point downstream of the L/R selector switch that's upstream of the Front/Rear branch.
As I'm sure you know, Amber running lights are not legal in the rear so the rears wont be configured for running lights.
I could use red for turn/running lights but want to keep the Amber as it's a safer choice.
I'm not in a big hurry to do this as the 1157 LED's provide both running (reduced lum's) & turn (@ full lum's).
I'm pleased with the effect at night but want full output in day time for inhanced conspicuous.
Still need to install 4 more Oznium bolts in the hand guards (2 forward & 1 to each side).
I have an older BMW RT that has a Kisan SignalMinder that provide running light/turn signals that are configurable as well as an auto cancellation feature.
I WISH I could install a similar device to shut off my turn signals on the Zero.
Eventually will install indicators or just one with diodes powered by the turn signal cuircuits and put them in a location that's more apparent then the ones in the dash.