The project you have in mind would be a labor of love ! Still,I do not kow how one can by-pass at some point needing to buy some of the books or even if one ought to. No serious seth student can live by quotes alone :-). Its true with kindle one can only search on book at a time but what a difference it makes from using that stone age thing called an 'index' :-(. Its all new to me so yes the kindle thingy would be on PC too
The context aware feature would help, though that is somewhat adressed by having the kindle quote in its context and being able to read backwards and forward.
The only down side of Kindle is that one has to have the device, the app, and the money.If you can do what you have in mind without triggering a 'wailing and a gnashing of teeth' over copyright you shall inherit the kingdom of heaven.
My next trick is to see how if I can find an app to turn a kindle book into an audio file, cos ain't nobody reading TES on youtube yet and some of those TES books are dense, esp 8 & 9.
The stuff I found on the brain last night kept me awake, the brain awakening like a leviathan