Thanks Philippe, and thanks Kenny for posting the vid!
In the meantime I also have some news for (potential) FF210 owners, with regard to converting to 12mm hex and with regard to compatibility with the DEX210V3 kit.
There already was a #7082 Rear Axle Conversion for 12mm hex axles; however I found it is not only compatible with Associated B5-series axles, but in fact the DEX210V3's 12mm hex front axles are also a straight fit.
Using the narrowest setting (1.5mm spacer on the inside of the axle, the 'STD' setting in the picture below), the car will be 4mm wider in total compared to using the Associated axles (91406).
The car's stability will increase - particularly for high grip - and at the same time it stays within the 250mm required by regulations. I have already been running 2mm spacers (per side) on the rear for a while with the Associated axles, so I have experience with its positive effect on the handling
So you can achieve the widening effect with the Associated axles; the DEX210V3 axles just add another option to the list when converting to 12mm hex.
With regard to the front end, the FF210 uses the DEX210V1/V2's axles. The DEX210V3's 12mm hexes are not compatible with these as standard: they are too narrow. Spacers are not an option because of the way the hex is constructed. I stick to my advice to use the Associated B5(M) hexes with a 0.5mm shim between the bearing and hex (image below).
As for the multi-axle CVD system of the DEX210V3: It is not compatible with the standard FF210 C-hubs and steering arms. I am looking into designing a version that is compatible with the multi-axles, however I cannot guarantee success at this point. On a positive note, the V3 kit I received recently contained all V2 goodies bar the bodyshell, so as was suggested in an earlier post, the first batch V3 kits have the necessary donor parts inside to build the FF210