It's pretty much already like that. Just take a look at the NES accessories.
I don't generally track my accessories, because I have like 10 snes controllers, 2 snes adapters, and 7 nes ac adapters, but I only own 3 NES and 4 SNES.
In my collection list, if I have multiples of something like a PlayStation controller, I just list one item and put "I have four of these" in the comments.
Not a horrible idea, but I actually use the android app a lot and it doesn't show notes.
Also, my mindset is elsewhere. I'm using the database to price my collection for insurance and developing an application to do that for me, taking notes into account complicates thing, but once I get there that might just be what I'll have to do.
But on the other hand, if you consider one controller a part of your collection, why not count the other 30 PS2 controllers. I have a lot of controllers for no reason at all.
LOL...that's more on the extreme side of things as far as my collection goes! It's just what works for me and honestly, I don't have 30 PS2 controllers!
For my personal tracking that is just for the sake of my old mind not working well any longer, it works best for me. Obviously, things like different colored memory cards get their own listing. But If I listed every double I had such as five copies of each issue of Walmart Gamecenter Magazine, I would have another 300+ entries for all those doubles. Likewise, I don't count bundled games separately from the console they come with. Otherwise, I would have doubles of Uncharted the Nathan Drake Collection and Destiny the Taken King as two of my PS4's have them bundled in.
It's always interesting to hear other's viewpoints on things. But back to the OT, if that example power block wasn't sold separately, then it shouldn't count as a separate listing IMO.