my exterior is Atlas Blue so it carries the outside theme into the interior
I think it will only look good with blue car. Colors are individual preference, but too many is not going to work out for all. Blue ST already have blue and red bit, so that stitching won't look out of place.
My ideal ST would be red exterior with red stitched interiors. Logos, Ford performance sill plates have some red already. Also need all the silver bits in the interior in carbon fiber finish (from factory).
Second choice would be the above one with black exterior color. Even though it's my favorite color, the high maintenance required, will keep it as second. I still drool at all the fully blacked out STs out there.
Coming back to ST appearance package, even on my Atlas blue, I would not add it for an extra cost. Only because the default white one goes well with the silver interior bits.