I am also intrigued by the FM approval. I am also kind of surprised they didn't allow it back in the late 1990s when Europe standardized 4 watt CB (FM mode) using the same US 40-channel CB channel plan as the de facto European standard plan.
Considering how many export rigs / 10-meter rigs are out in circulation, there might be quicker adoption of FM than you'd think. Even the basic 240-channel 25.615-28.305 MHz exports made by Ranger/RCI - think Superstar 3000, Connex 3300, Galaxy DX 33, DX 29, dozens of others - yes, your old Dirland export rig is included in that list! - have been AM/FM radios since the 1980s. Yes, there are/were some AM-only export rigs on the market and a few AM/SSB only ones too...must most of them had/have FM mode in addition to AM. Even the humble Superstar 121 has FM mode.
Of course, all the modern style Chinese export rigs have FM capability too.
I imagine there will be an increased demand for FM add-on boards for AM only CB rigs like the Cobra 25 / Cobra 29 series and related Uniden PC66XL / Uniden PC68 series and PC76 / PC78 series...if FM takes off. I know that AM/FM versions of bare-bones AM CB radios like the Uniden PRO510XL and PRO520XL are/were sold in Europe under the President name so it's probably not too difficult for US market versions to...well...come to market.
What I'm interested in seeing is truck stop CB shops and the various CB upgrade/tune up shops offering FM CB boards or FM mode add-on packages or upgrades / FM mods for FCC-legal 40-channel AM CB radios that are currently out there in the wild. Turn your AM CB radio into an AM / FM CB radio!