Food for thought
Your original plan wasn't bad.
Just had some room for improvement, depending in what area you wanted to focus on.
re Ecoda 22khz: I thought you might try powering your 2100 through your switch.
Many diseqc switches won't handle the current.
I never recommend using a switch ahead of a motor, but some users insist on that configuration.
The Ecoda 22khz was shown to handle the load, along with a few diseqc switches.
About all I have to say on the matter.
re Ku dish size: if you are happy with a 76cm on a 2100, that's fine.
But somewhere down the line, you'll find some stations need their own fixed dish...often a bigger one.
Instead of making a decision in the dark, why not put this aside and come back to it later?
There are just too many variables and choices; leave room to change your mind.
re molded dishes: my favorite kind.

the 90cm would be an improvement, but the weight would call for a more robust motor.
I'd outfit it with a Standard PLL LNBF.
The oval Primestar would be best if you kept the matching feedhorn.
But unless it was the larger 84e, you'd be better off with the 90cm molded.
And it would need a robust motor, too.
When/if you are ready to spend money on a big Ku dish and motorize it, a safe choice would be the GeoSatPro 1.2m and PLL LNBF from SatellliteAV.
I'd stick that on a STAB 120, and be done.

There are a 100 other ways to skin that cat.
.