Further down I discussed (wrongly) being prone or upright and why thats not feasible.
For the idea to look over, how does it work when the furniture you look over stands at the edge of a multi floor building? How are you gonna determine Line of Sight for Z levels below?
And for my first answer, which missed your suggestion;
I am not sure how being knocked to the ground is being handled. I think its more of a ‘cant move’ status with a specific message.
Moving even in two positions (crawl and up right) would increase the options of moving in any direction at an exponential rate. From what is now 9 + 2 (cardinal directions plus up and down) to (9 + 2) * 2.
Think of all the checks that may have to be Iterated every turn. Whether you fall off a building or something.
All those functions would have to now consider your moving state (upright or prone) for every action that involves movement.
Thats likely to break something.
And what to show for it?
Unless implemented from the start (or in the uncomprehensible ways Tarn Adams did what he does) this wont turn C:DDA into stealthy Metal Gear Solid anytime soon