I'd love to be able to select images based on interval. I had an issue with an irregular interval, and I had to manually select about 1000 photos. I'd love that as a feature, it would have saved me a lot of time.

I have this on my list.
Often in such cases (for example if you have double images because you forgot to set "Single Mode" on the camera, you and for example you want to delete every 2nd image in a range of certain images, you can do the following:
1.) Select the Range where every 2nd image should be removed
2.) Choose "Edit/Select every nth image" from the menu
3.) Set 2 as distance an 1 as offset, this will select every other image (the obsolete one).
Right click on a selected image and delete or remove it.