I seem to recall that the inability to embark in certain areas with large troop units was, if not intentional, acceptable. It may not always be possible, for example, to find ships to carry 100 cavalry troopers in rural regions, or remote badlands. Especially in enemy territory. Doesn't seem to unrealistic to me.
Then it should say "you can't embark here," not "you can embark here if you have more hours than is physically possible (except for a priest)".
