Here's an idea... ADSB is required mostly in rural areas. The cost for an ADSB-in receiver in conjunction with a satellite dish install is bugger all.
On a few country properties, tell each cocky we're going to install another bit of gear with your dish, and we'll pay you $50 a year to cover the minimal additional electricity bill and the minimal amount of data generated. 1000 sites, $50K a year "royalties to farms" plus equipment replacement.
Bam - nation-wide ADSB coverage at lower levels.