Jim were you aware that you can lock AE when the focus is locked on the K-30? I was just thinking about changing to the rear focus button to give it a try and came across the info in the manual. It may be of help to you in your situation so I thought I'd mention it.
You can find info on it on P.94 in the manual and you need to turn the feature on in the 'Custom' menu, Page 1, Item 5 (i.e. C-1-5).
If I understand the manual correctly (and I may be wrong) when you get a focus lock then the AE is locked too. I haven't tested it but that may mean you could use the AF/AEL button as the rear focus button and still get the AE lock you require. It would also mean that you get AE lock every time you focus of course which may not be what you are after.
I would also assume that you could assign the settings to a User Mode so that you can revert to normal operations when you wanted to.
Last edited by Tako Kichi; 05-24-2014 at 11:55 AM.