Very new to the forum, but am also a networking guy so I have a fair amount of experience with wireless signals...and the P4 uses the same frequency that wireless networks use.
Most of the mods I've seen out there don't actually change anything related to the power of the transmitter. Different antennas will have some effect just based on the relationship between electric current, voltage, and power but even the antenna replacement kits still plug in to the same xmitter module on the drone. They mostly deal with focusing the transmission in one direction (toward the drone), whether that is through external parabolic attachments or flatpanel antennae, and gives a stronger signal (in that direction).
Outside of changing the internals on the drone, I doubt there is much you can do from the AC side.
But I'm definitely not an expert in RF.