The point of the ritual system is so that not one person can solve every single problem during an encounter with magic.
It is part of what made wizards so powerful in 3e. It wasn't fireball. It wasn't magic missile. It was the ability to adopt to any situation by having the right spell at all times.
What you propose is to bring back that utility to a single character, since all they'll need is the incantation book.
The rituals are non-combat spells for a reason. As written, rituals are a party resource since everyone can aid the skill check and provide the components.
I suggest trying to run the rules as written for now before fiddling with it. The scenario pointed out (party trapped with a locked door) has many solutions already pointed out without introducing a potentially unbalancing mechanic.
While my example doesn't show it, the skill check is still a potentially cooperative thing.
Sorry, guess I need to spell out the complete mechanics, but did not want to (and am not sure I am really allowed to) detail the complete mechanics since Incantations are a exception-based version of Rituals (i.e. the rules for Rituals apply except where Incantation rules explicitly override the existing rules.)
Incantations may not fit in every DMs world view. That's fine. I'm just working on a balanced mechanic and asking for criticism.
Your points are well made. However, I think I (we, since this is a PEACH) can find a way to make this work without breaking things.
I think the uncertainty of casting and potential of a botch or interruption is the good beginning to finding the balance I am looking for, although I just though of something I missed in the mechanics. Time for another edit.