First move your force sensor to the other end of the boden (move the mass to where it doesn’t matter).
Second add spring elements to both the boden AND the filament.
I feel you are underestimating the amount of elasticity in the system. It could work but I feel the time required to “adjust” the filament force is going to end up slowing things down.
Another consideration. The force created by the “big” motor must not be so large that it overwhelms the small one. Unless you use a high reduction worm gear train this force has to be smaller than the maximum force the small motor can generate. This limits the total filament force into the melt zone to around 1.75 the small motor force.
I have seen extruders with worm gear drives but AFAIK the backlash was so bad that that design was abandoned.