Request is to implementing additional input not less.
Finger input can already accomplish:
Pan, Rotate
Rename
Input calculator
Name Variables, change variables
Strangely I can select a face by double tapping
Only thing that the Finger can’t do is:
Drag to select
Select objects
Drag dimensions
With variables, inputing by typing could be more efficient on a tablet with some of these last features unlocked, since accuracy can be solved with variables.
I’m guessing here, but as a former app developer for many years: The pen separates user intent in a clear way. If you could use your finger for everything, then it would be a balancing act of sizing the touch areas just right, counteracting multitouch events all the time and fighting various user requests of interaction results, which always results in a compromised UX.
Example: 2-finger pinch zoom and model covers entire screen. Now you want to touch-drag a point, but accidentally rub your knuckle against the screen and zoom out instead. Should the point be reset or left in the new position?
Some would expect it to be cancelled, others would be annoyed a zoom was initiated in the first place and a few would be utterly confused. Separating intent with the pen makes the experience more stable IMO.
I also developed custom touch interfaces for trade show displays and games in VR/AR/IOS so my suggestion is coming from that experience. Trying to figure out clever ways to make touch easier or figure out clever engineering solution to compensate.
Throughout using various iOS/Android/Surface Windows apps I have not encountered a mainstream design app that disables touch inputs, if something is not possible or practical they give you alternative. I feel like if you let touch work user will know to upgrade to a pencil. Example, you don’t need pencil to draw on Affinity Designer app but it’s nicer on a pencil.
Right now there is navigation presets for Mouse/Trackpad why not add Touch/Pencil let user toggle it off or on. Also Shapr is not really utilizing all the Pencils features like, click/haptics so its just a dumb pencil, if that’s the case why not let touch work so you can buy those cheap capacitive pencils so I can freely misplace.
Here are some apps for touch inspirations:
Affinity Designer for delicate selection it brings up a magnifying glass above your finger.