Well, after some further investigation, and talking in a couple Ajax IRC channels, it is confirmed that an Ajax pure front end would be a bad idea. I am still going to continue our development of a complete Ajax back end, I believe it's worth the blood sweat and tears, plus lack of sleep, and keep our front end more of the classical 'web site'.
Personally I feel Ajax would be an ideal solution for a complete website, not just web apps. Just imagine how much more attractive all of your own personal websites could be (I just imagine everything I'd never expected from a 'normal' dynamic website.) Of course an engine must be there and geared with the thought that it will be interacting with Ajax. Though, Ajax is after all, just a means of implementing a user friendly, modern geared, UI for clients/users. So I don't feel that Ajax should only be used for small little gizmo's I'd want to 'spice up' on a CMS. If I wanted to settle for that I wouldn't even consider Ajax, I could just stick to few little JavaScript functions to accomplish that.
I do also understand how creating SE friendly URI's to pass variables is a must to ensure ranking and crawlablity. SEO is a large part of our business, and is why client's come to us. Thanks for the tip on the static HTML archive, I've considered implementing something of the like as an optional module in the past, but we still havn't ran into a situation where it would be neccessary, but I'm sure we could get creative with a simliar feature.
Thanks for the input. Happy coding.