I would be very happy to fit FLARM, if it can get to critical mass for most flying machines. It has the big benefit that almost all could use it and all would benefit. I get zero benefit form my transponder.
What? But you most certainly DO get a benefit from a transponder! It enables those in receipt of a radar service in Class G, or those using an ACAS system to avoid you, in good time, keeping everyone safe, including YOU and all in YOUR aircraft! Many of the ones that have avoided you already, to date, were possibly never even seen by you because the avoidance taken would quite possibly have put the other aircraft beyond the human eye's effective visual range, certainly so in IMC.