Hi there,
1st off let me say I am quite pleased Plex. Everything is not perfect but at least good and more importantly I have the impression the Plex people, albeit silently, pay attention to users feedback in order to improve the experience.
Now the consequence in my case is that I will most certainly deploy a plex system at my mom's. PMS on a Raspi2 (likely), iOS app on iPad (certain), iOS app on appleTV (likely), PMP or PHT for mac (likely), and plex web (certain).
What I would like is a simplified user interface (I haven't seen the aTV app yet)
In order to delete buttons and simplify interactions I imagine it might be possible to add (per-client) preferences to PMS. For ex: never transcode (direct play only), prefer AC3 on client XXX, prefer original audio language + fallback to lang. XX, prefer subs in lang ZZ, auto-queue remaining TV episodes ...
And let's not forget: larger fonts and less elusive sliding panels.
I believe such an enhancement could target both the grandma and kids market segments. Premium stuff ;)