Scaling up the map like that will also mean that its a lot more complex to cross the "lake". It'll go from maybe 10-12 km across to something like 60-100km across (wild guesstimate). more an inland ocean, really. Still, it also makes it more plausible for people to get away by crossing it. or for that matter, to go out onto it.

We'd also think that this would mean that there are a lot of waterways not shown on the map. Even fairly large ones. a river 50m wide, or even larger would be invisible on such a map without having a massive spiderweb of blue threads. Those rivers criss-crossing the Empire are probably large enough for massive ships to pass beside each other without any trouble. 

By the way, Sep. If you're working on turning Ulior into a new place (or whomever might do that), we'd recommend taking that island in the lake and putting it to good use. Stick a few cities there. maybe even a massive metropolis. Properly fortified, it'll be a hell for anyone to conquer, evokers or not. You could have walls high and thick enough to stand up against most any barrage. Evokers like that fellow striking at inner city gates would not be able to do much against such. 

One more thing... if anyone is planning some city or such... We'll not mind at all helping ya determine defenses, even defenses that are suitable to stop Kalesian assault. (its fun throwing wrenches that potentially mess up our own plans). However, we'd rather not get involved in controlling the defense of Amaryth, or any other city the Kalesians might choose to strike at. Designing it is ok, controlling it not ok.

EDIT: interesting character you crafted, Crab.