Hi Siamsa!

I think you should definitely go ahead and email this potential supervisor of yours. There's no harm in seeing what their opinion is, so why not! Only thing, perhaps, rephrase the your Q. 'would you be able to supervise...', instead suggest a meeting to discuss the possibility of them supervising your PhD, cos it's a tad unlikely they'll reply 'yes' in an email ;)! Or maybe I'm wrong!! Also, if they do agree to a meeting, I'm sure, they'll be able to offer you some sound advice and expertise on what to do next.

Hope it works out well for you :) and my words are of some help!

[Oh, a little side note: I emailed a potential supervisor the other day to see if I could meet them to discuss the possibility of beginning a PhD this year. Just got a reply saying they'd be more than happy to meet me! So, there you go!]