the intire point of a handheld version of the switch is to do it cheaper (to capture the handheld market).
That means useing less parts.
Which means No "joy-con" attached.
The controls need to be fused on the handheld, like it is with all the other handhelds.
Its cheaper that way.
Which is key for the viability of this device.
I mean a handheld only switch, wont sell if its priced the same as the normal nintendo switch.
Basically your concept sounds bad.
A handheld version of a switch just wouldnt be able to play most of the games the same was as the switch.. ei. the local co-op mulitplayer with the joycons.
But honest how big is the demand for that on a handheld? probably not big so its not a issue.
The price of the device is much more so.
299$ if your only intrested in useing the switch as a portable, is way high, compaired to what handhelds normally go for.