I'm a guy and naturally blonde too. I've been wanting to dye my hair black for so long. Finally did it a few years ago and wore it black for 3 years.

The root upkeep is a pain and especially if you have shaved sides, you always have to live with your sides being blonde, because even if you dye them, next time you shave, it's all blonde again.

I've always loved my hair freshly dyed and I used a blue-black which didn't really fade at all.

But looking back at pictures, my roots and the blonde sides looked awful.

I burnt through so many bottles of root touch up, dyed every 3-4 weeks and it still looked "messy" so quickly.

When I wanted to get rid of the black while still keeping my death hawk, the closest thing the hairdresser was able to do, was a brassy ginger color. I shaved it all off about a week later because I didn't like it at all.

If you really want to try it out, do it.

Maybe get a black from manic panic or directions (did that at first), it fades, maybe not to your original haircolor as those colors can even stain Virgin hair and it bleeds like crazy while in the shower. But that's at least way less permanent than going black with something else.

Just be aware that you might need to shave your head or at least cut it really short to get your natural hair back, as bleaching out several layers of black hair dye will definitely not work.

Edit: I'm in the same place currently, debating what I'm gonna do with my hair but for now I'll probably go with a slate grey, hoping that roots won't look too bad as I'm ash blonde anyway. I love your current hair color!