Personally would like to see him played more and used more efficiently (support shen is really good).
The main thing i wanted to post about was his ult. I don't like it running off ap, i would love to see it run of %of max hp, because most shens are built tanky with little ap or ad. Maybe like
Active: Shen begins channeling for 3 seconds, immediately shielding an allied champion for up to 5 seconds or until it is destroyed. If the channel completes and the target is still alive, Shen teleports to the targets location.
No Cost :
Cooldown: 190/170/125 seconds
Shield Strength: 250/500/750 (+0.4 per ability power)+(4/5/6 % of maximum hp)
I tweaked the cd just a bit higher because the shield will be a bit stronger, lower ap ratio as well because then he will be op, and base strength lower at higher levels.
Also this means he can build the amazing new rylais much easier because of the hp ratio, much like his passive and Q heal ratio, meaning top and support shen will be more common.
Give more ideas if you can!