So I am making my first wedding cake; fortunately it is for my nephew and he knows it's my first.  They have asked for an ombre cake.  I've visited the venue (an old historic home) and it is not air conditioned; the wedding is the end of June (in Chicago area).  So I will be doing a fondant cake.  Below is a picture of the effect they want to achieve on the cake (although this is done in bc).

To get straight lines on the cake I plan on arranging the strips on parchment paper to then apply to the cake.  The cake will be against a wall so it is okay to have a seam in the back but I would like to minimize it.

My first concern is rolling the strips in such long lengths.  I will use my pasta attachment on the KA (unless someone has a better idea) but I'm worried about handling the strips for the larger layers.  The cake will be 12-10-8-6.  The top will have flowers and I do plan on making a whole lot extra just in case I need to drape some down the cake for cover-up.  Should I make the strips thicker, maybe a 3 on the pasta roller?

My second concern is covering the sps plate.  I usually use just the cardboard rounds and dowels but I thought for this I would use sps so that I don't have to worry so much.  I want he bottom row of fondant to cover the plastic plate without having to put a boarder on (but just in case I will be prepared to put on a boarder!)  I don't want to cover the cake on the plastic plate because it seems it would be easier for me to mess up the fondant when putting the plate on the pillars (it would make more sense to put the plate on the pillar and then put the cake and secure it and the put on the cake).  So any suggestions would be helpful.  Thank you!

AI would bake, fill, crumb coat, put each tier on the sps, ice with buttercream, stack, then fondant. Use a rolled up piece of fondant for the board, pushing it up to the cake and smoothing. Then add the bottom strip of fondant to the cake, making sure it meets up to the board. Line each additional strip up on greased parchment before applying, to keep them straight. Top the tier with a strip, bending it as you go, butting it to the edge of the next tier, making sure it comes to the edge of the tier it is sitting on.

Also, some math and measuring will be involved because you will want your strips to precisely fit the sides and be even. All your cakes must also be the exact same height.

Thanks Anna for your suggestions, that makes sense to do the fondant after the tier is stacked and I hadn't thought of the rolled up fondant on the bottom.  I also hadn't considered the math so thanks, that would have been a rude awakening for me!  And thanks Remnant for the encouragement.  I'm really looking forward to doing this.  Using a church kitchen which I just went over and checked out.  There were no grandkids there, this should be great!!!!
 

Also, if you're concerned about the SPS showing, you can use a 1" smaller plate for the top 2 tiers.  It'll still support it with no problem - I do it everytime!  Good luck!

I want to see the final product...based on the advice that you have gotten I can tell it's going to wonderful!