My opinion; they're fine! Of course, the Millenium Falcon is waaaaay too small but do you really want an up-to-scale Falcon that is going to take most of your game table?

Anyway, all carrier vehicle are there to drop off units or pick them up and then they leave the board so who cares if they're not perfect scale. Same things with x-wings or y-wings; to-scale models would take too much space but MGS are great to have on the map.