however I think it's better to integrate this into the existing open dialog. Perhaps with a checkbox ([x] open recursively)
I think I tried to do that initially, but I got into some issues that made me decide to just use another dialog box. It's probably the difference in behavior between targetting files, and targetting both files and directories. I can't remember if it was the stock button or the dialog box itself that's to be blamed.
Anyway, I find using another dialog box more convenient and faster to use. I don't have to click a checkbox, or check if it's been activated or not before clicking a View or Open button. Differing behavior, and programmatical issues that might occur are also segregated.