Vent Relocation

I'd appreciate some insight from the experts before I make a fool of myself with the county planning office.

I'm remodelling a second floor bath. (The 40 year old tile, lead drain pan, and subfloor have disentigrated. ) I'd like to replace the shower with a tub/shower combination, but upon demolition, I discovered that the main vent stack had been hidden behind a boxed-in space adjacent to the old shower. However, the vent stack and and associated 2" vent rising vertically from the toilet drain are both about 12" from the exterior wall. Only if I can "jog" these vents towards the exterior wall, will I have enough space to install a tub/shower. There looks like there is enough room to divert the vent stack horizontally between the floor joists above the toilet connection to the vent/soil stack, but below the subfloor. Near the wall I'd route the vents vertically again until I reached the attic where I'd jog them back towards their original position and out the roof.

Would such a horizonal vent route violate some of the code issues concerning venting at least 6" above the flood rim of all group fixtures?

If so, what are my alternatives?

I'm not a professional plumber so please be patient with my terminology.

The next floor can't tye in below 6" above the flood level.

However, you can jog the vent back into the wall and then tye the next floor in at 6" above flood level.