Not sure I follow you Cab.
By allowing the front spring eye for and aft movement, you alleviate the contradicting arc movements of the ladder bar and leaf spring.
Sliding the front eye eliminates the cost and wght of the floater.
elongate the hole in chassis 1/2" fore and aft of original hole center, reinforce with some thicker plate above, below hole to support eye bolt as it slides.
at that point, the spring just holds the car up and the ladder positions it.
Dont know what you mean by saying the floater allows the rear end to move up and down.
Once the floater is installed, the height is fixed, some have hgt adjustment.
The floater allows for for and aft movement thru its pivot.
As long as there is freedom for the leaf to move, the binding problem caused by the 2 conflicting arcs is a non issue, no?