I really like your color and pattern choices!
This will be a work of art!
Now that you mention it...I wish I had knit the vertical squares into "columns" all together, then all's I woulda have had to seam are the "columns"!
I made this for my granddaughter, and my oh my, seaming all those squares! Phew. But what I did was: seamed all the vertical squares into columns...then seamed all the columns.
Your idea (alas, too late for me) is great!