I suggest shopping around for sheet metal manufacturing companies. If you can handle the design yourself and make their life sensibly easy to work from your data, there won't be problem to get economical offers even for singles qty. If lead times in 3-6 weeks range are an issue, you might consider investing into simple sheet metal bender and handpress, laser cutouts are usually doable in one week turnaround with no price extra.
Clinched fasteners win almost every time - just for the love of god please never use loose nuts anywhere - if totally desperate to have it removeable, use caged nut insert instead. For rework there is option of rivet nut.