can confirm the dpi buttons are programmable. the button underneath the scroll wheel is unbound so you can program that to cycle dpi or be a profile cycling button. however, in the latter case, you must make sure it's set that way for each profile or you will not be able to cycle anymore.
however, do note that only a single profile can be saved to the mouse. so if you create 3 profiles, and set the button underneath the scroll wheel to cycle, it won't work without the software running. only a single set of static colours and other settings can be saved to the mouse's on-board memory. I think you can create more profiles than the g502 though.
the G502 also has two buttons in the exact same place, but also has a scroll wheel that clicks three ways. unlike the corsair mouse, the g502 can store three sets of profiles in its on-board memory, so theoretically you can set three different button combinations, which you can cycle through with a button. unlike the corsair mouse though, the logitech software will force any button you set as cycler to be the same for all profiles (which just makes sense, but I thought I'll mention it).
logitech also has one above the g502, the chaos spectrum, which may prove interesting to you. it doesn't have as good a configuration of top-facing buttons, but does possibly provide one button more through having two banks of configurable sets of side buttons or side button bank covers. I don't have that mouse personally so I can't say how easy they are to reach with fingers. maybe only the frontmost one would be realistic. which would tie it with the g502.
I think perhaps you should have a look at this fellow right here, and perhaps see if you can shoot an email or other communication off at the folks who reviewed them to see if there are any like them.http://gamingshogun.com/2016/05/31/bloo ... -a-review/