Hi,
The more things you add the more probable failure will be…
Most cameras today have electronically operated apertures, as electronic control is needed for fully automatic exposure. Also, we really want view and focus at full aperture and expose stopped down. So, some version of automatic aperture is needed and it has been a standard since 1960-es.
Just some oil on the aperture blades would stop the automatic aperture from working. To put it in perspective, I have been taking pictures since 1965 and had something like 50 lenses until today and aperture only failed in one. Bayonet needed replacement on a 1985 generation lens and automatic aperture failed on a Hasselblad CF lens I used to have. Other than that I had no lens repairs/failures.
I guess that modern lenses may be more prone to failure, though.
Lenses that are used stopped down all the time (like Leica M-lenses) may be less prone to failed aperture. But I know of some cases where Leica S system had malfunctioning apertures.
The way I see it, any component of any system may fail. 2012 I was on a trip to the US, my tripod mount on the 70-400/4-5.6 G got stuck and my brand new RRS tripod came all loose first day. I could repair both in the evening…
Best regards
Erik
Any reason why it can't be mechanically linked to a focus ring, rather than relying on an electronic link?