Tunic ---> Skirt

I have this khaki colored button-up tunic from Old Navy that I have not worn for a while. I used it a lot last year, but not this summer. Problems with it: It is just a little too short to wear without leggings. I love leggings, but they are really hot in the summer, especially since our house doesn't have AC. I also don't really want to wear leggings to work, so this tunic has basically been wasting valuable space in my tiny closet. I also recently noticed that I have almost no solid colored skirts. I have maroon, black and brown skirts, but besides that nothing. All three of them are full skirts, the maroon and brown being three-tiered gathered skirts. I like loose, flowy tops but if I wear anything like that with these skirts, I feel like a shapeless bag. So...I mention all of that to say that I'm thinking of converting this tunic to a skirt. Something more along the lines of a pencil skirt. I'd like a high waist too, so I can tuck my shirt in and wear a cute belt. Because my tunic is essentially a super-long blouse, I'm looking for tutorials about how to convert a blouse or man's shirt to a skirt because it is the same idea. I found a great tutorial over at Hawadaere Blog, here. I didn't want a zipper, and I was trying to think of a way to use the buttons and button holes already in the thing to fasten the skirt at the waist. So...I would totally follow the tutorial and do it today except that...
...She recommends that you cut the cuffs off the sleeves to use for the waistband (this is how you get the pre-made button and hole) and then just cut fabric from somewhere else on the item for the rest of the item because for most people, including me, 2 sleeve cuffs do not equal the circumference of the waist. The only problem I can foresee with this method is that there will be seams in the waistband at rather awkward places. Instead of having seams on each side, I think the seams will fall more in the front, with your long extra piece covering more than half of the band. This might not bother some people, but I really would rather have the seams at normal, even places.
So I need to think about how to deal with this. Most of the other tutorials I've found either require a zipper or interfacing (which I don't own and stupidly forgot to pick up at Joann's Fabric yesterday.
I'm just going to think it over for a few days before doing anything irreparable (like cutting my tunic in half...) because I have a habit of starting projects without thinking them through properly :-/