the problem is alot of people like the standard control panels, such as cpanel an directadmin, because they no what it looks like, and how to use it, but if you are able to make one, and implement it, and does the same kind of thing i think you should do it, also think of the money you would be able to save per server
As already said most like to stick with the likes of cPanel because they are familiar with it. If your selling hosting it may affect sales not offering what folks are used to. However newbies to Hosting wont know any different anyway so I guess ite depends on the market you are targeting.