Petar, Just some random thorts hope they help.
You will have to pick a user market Hobbyist, Education, Advanced but poor user who needs high performance. probably the list is endless because in reality you will be selling on price at the lower end almost certainly. If you want to sell to Pro, Labs etc with big budgets they will pick the Agilents and Tektronics of the world.
You could have a unique feature, features that will offset selling price a bit. may have many different grades of spec as well, seems common in the O Scope business !!
Stand alone unit or PC Card ? Its not very easy to plug a scope probe into your pc under your bench or even on top of your work area.
so that leaves stand alone box etc. USB / LAN to PC, even blue tooth if you are only using the PC as a display device / controller you only need to update the screen at 60 Hz all processing / storage and capture in the device. Basically a full scope without controls or display.
good selling point could be design your own interface, twin screens.
Custom build your own or open source hardware external control panel with real rotary encoders, switches etc with USB / LAN or Blue Tooth this would appeal to hobbyists who want a project but would not attempt an FPGA Scope.
Just my random ideas.
I can't help feel at the end of the day it will come down to competition with the mass production / price of the Chinese manufacturing power house, unless you can get a slow
gradual relentless Hobby, open source way to volume supplying. with firmware and parts, main logic board as a kit.
I hope this isn't a rambling load of old tosh
All the best to you.