That sounds like a great system. If you want to fly your drone in controlled airspace, then you should have to have something like that on it.
Nonsense. You shouldn't be in a place where you endanger manned aircraft in the first place.
In the second place, that system depends on ATC providing traffic separation services to the manned aircraft, which they do not do for VFR flights.
Third, it depends on the pilot actually seeing the target to avoid it. Smokey air, turbulence, pilot busy flying and looking for the drop site, not a very good recipe for seeing a small drone before it hits you.
Fourth, it depends on the area having radar service. No radar service, transponders don't do anything. If you are low enough to get good video of the fire, you're probably under the radar coverage area.
And finally, the weight and cost of putting such a system on a DJI Phantom, for example, would make the drone unable to fly.
Last I checked, it was possible to make antennas directional,
Yeah, the directional antennas used for the transponders are those huge spinny things you often see near airports. Actually, the largest spinny thing is the primary radar which depends on the radio echo. The smaller spinny thing mounted on top is the transponder antenna, called secondary radar. Very large and very not portable. You won't have time or ability to set one up near a fire site, and if you did you'd have to worry about coverage. You have to have them in the clear so they can see far enough to be worth it.
It's not a feasible solution to this problem. It's a solution suggested only by people who hate drones to the extent they want to see them eliminated from the skies altogether.
you're being snarky because you're really clever
I'm telling you in a polite way what a ridiculous idea you have and that putting such a transponder on a drone will not keep them out of the way of manned aircraft and will not allow manned aircraft to avoid them. When you are a pilot on a firefighting aircraft you do NOT want to be distracted by trying to identify traffic that may collide with you. THAT IS WHY THEY PUT A TFR UP IN THE FIRST PLACE. It is a big KEEP OUT sign intended to make the operation safe enough to continue. Other aircraft in the area are a hazard for which the only mitigation is to stop flight operations until they leave.