Look for a Durst M600.
And the key...you also want the original BOX. I have a M600 and it packs well between sessions.
Setting up and breaking down the enlarger is not difficult. It is like it was designed to be taken down between sessions.
I know you can do 11x14 with the M600, I did.
I do not know if you can do 16x20 w/o rotating the head to do a wall projection, or rotate the column and project onto the floor. The M600 can do both of these, so you can print BIG...if you want to.
I do not have experience with the other medium format Durst enlargers like the M601 and M605. But I would guess that they would also be able to be broken down and stored like the M600.
I also have in storage a couple of Omega C series enlargers. Setting up the girder on the baseboard is much more difficult than the Durst. And the box is much longer than the Durst. Although you can stand it on end in the closet to get it out of the way.