I know the Ariadne well. One of my friends use to distribute Maplenoll TT's. The air bearing linear tracking tonearm on the Ariadne was an early design by Bruce Thigpen of Eminent Technology based on the ET1.
The Eminent Technology ET2.5 air bearing arm is substantially better than the version on the Ariadne. Even a second hand ET2 would be a substantial upgrade.
Since the ET2/2.5 has a similar footprint to the Ariadne arm you should be able to install it easily - at worst you might need to make an adapter plate with different holes to mount the ET2/2.5.
I would strongly recommend this upgrade - the ET2/2.5 is much easier to set up than the Ariadne arm and much better sounding.