I seem to remember a comment that FLARM with its variants is a private initiative of one company, who reserve the right to change the communication parameters of the system at their discretion, and force users to payable upgrades.
If this really be the case, it is a NO NO for me. Can anyone confirm, or gainsay?
Any safety-related matter and equipment should conform to protocols and parameters under public control.
As I understand this is the case for ADS-B. The best compromise I can imagine is to transmit one's own information under an "official" format, like ADS-B or mode-S transponder, and to receive and display information from as many sources as can be managed.
Linking to another thread: electrical power goes to transmitting, not to receiving. Transmitting in multiple formats would consume lots of electrical power, receiving and decoding and displaying several formats much less.