So I've seen people create the Lazy Mans 3x3x5 where they used a 3x3x4, sanded the middle layer in between the 2 layers to expose the hidden layer and put in a 3x3x3 edge piece and center piece to create the middle layer

This is the Lazy Lazy Mans 3x3x5, no sanding required, but you need to spend more money for parts...

This one is a C4U 3x3x5 where I took out the top and bottom layers, and replaced it with a C4U 3x3x4 top and bottom layer.

You skipped over laziest man's 3x3x5, the C4Y 3x3x5.

thats not lazy enough!! just use the 3x3x5!?!

TBH though, my lazy man's 3x3x5 is my favorite puzzle. I prefer it over a cubic one.

Could you combine the remaining parts and make a 3x3x4 with thin top and bottom layers?

Merlintocs, I don't see why not. Ill try when I get home and let you know =)
It might create a Cubic 3x3x4 =P

Cool I might have to try that.Is it harder/easier to solve than a cubic 3x3x5

Cooldayr made this and the 3x3x4 with the layers.

there would be no reason making the cubic 3x3x4 wouldn't work.

I'd say this easier to solve than a cubic 3x3x5, but only because you can tell when a layer won't turn, and it's easier to turn the top and bottom layers.