Why reinvent the wheel, why not use what apple already developed - the newton
Seeing the video, I think this is still too complex.
Remembering why my newton did, it was SO simple.
With the stylus, you
mark like this:
- tap + hold (a "plop" sound marks the begin of the action and the cursor changes into a round black circle the signifys the begin of the marked area)
- move to mark the text
- lift the stylus to end marking
and then you can address all sorts of commands to the marked section like:
- delete (scrible over it)
- move (tap + hold; move somewhere else; release)
- copy (double tap + hold; move; release)
- overwrite (just write something new and it will replace the marked text)
cut / copy to clipboard are actually just move or copy but instead of moving it somewhere else, you move it to the side of the screen and it locks there.
Paste is just taking the bit from the side of the screen and moving it back somewhere into the text. There are even 2 pastes, one with one tap that will move the pasted stuff into the text and removes it from the side and double tap, that will leave a copy in the clipboard.
ALL that is very visual and very close to actually handling a cut piece of text, no need to remember that there is a hidden clipboard somewhere and you can actually have multiple text fragments in the clipboard (the side of the screen).
And the newton did more, there was also the option to mark a rectangular section by just starting the selection in a free area without text, this way you could also mark drawings or text and drawings.
Great, And how to move this to the iphone? Easy!
- as tap and hold bring up the screen magnifying glas, just use the second finger tab to start a moving selection that stops with lifting the finger - easy.
- use a double tap to start a selection with setting the selection start, then move to the end and do the tap+hold, place the marker, then 2nd finger double tap again to end selection at the marker. done.
- And for marking a rectangular section, just tap+hold with the second finger too (after placing the magnifying glas where you want it), then move both fingers and a rectangular will start to appear.
You could even do stuff like if you only move the 2nd finge, it will become a circle with the first finger at the center and the second one at the outer edge. Lifting one finger will again stop the marking.
And removing the marking is easy to, just tap somewhere else

Removing a clipboard item is easy to, just move it to a NO DROP area, the icon will become a "no go sign" (or trash can) and it will disappear with a "whosh". You can even re-arrange the items by moving them around on the screen side.
Alle the other moves can be ported 1:1 from the newton.