The IPTC Stationery Pad dialog is used far less often and does require either typing Ctrl-I or by using the menus.
 i believe you said is far less used , but i  use the pad  on all the pics and the i  button only on some of them.
the i button is very useful , ... after i applied the stationary pad  on several pics 
they don't do  the  same function .
my problem  is exactly what you said : to have the stationary pad open  
require either typing Ctrl-I or by using the menus.
which  is  (in my opinion) not straightforward 
when i dowload the picture i mark them with different color depending on the  different  works i did that day, i select  al the picture of each color and i open the pad  which, in my case 
incorporate a general template which is modified on every group of  foto . so i'm  using  a the  pad on  every color   group of photo 
if you don't want to put more button it would be possible to personalize shortcuts; ctrl-I is a difficult couple of keys to strike at the  same time
thanks 
paparaz