add another criteria:
- this is engineering, sometimes, art, but 99% time/composition are definitely not science
- but this 1% science only determines how we use screw driver. so it becomes intuition eventually
here is my answer
1/ should be satisfied most of time.
2/ should not be a problem
i guess the difficulty lies on the width of two ground conductors, right?
if so, you can try to reduce the ground width. field attenuted very fast beyond the edge. this reduction also improves the efficiency. you know how slow FEM converges.
if ground width has to be THAT big, you can shrink the port width to be a portion of the enclosure lateral surface. there is one figure in CPW tutorial showing this.
let me see.. page 8, bottom right
this figure intended to show you, if the port is too narrow, substatial field goes out of the port region. this should not be a problem if port width> 3(2g+w).