Where's the market for that though? You're trying to capture the crowd for whom Photoshop via creative cloud is too expensive, so you have to charge less than that, but there's already a couple of open source programs that do some amount of image editing for free, so you'd have to be really near feature complete for your PS clone, which is a lot of tokens that could be used to fork those open source programs and make them better, rather than start from scratch.
I think if a good PS clone existed, Adobe wouldn't be selling so many subs. And yeah, undercut the hell out of it... How much does it cost in tokens to make the replacement?
The last time I was touching the PS world, everyone would laugh you out of the room for saying "GIMP". I had to pay for PS just so I could export art to use it in GIMP.