You need to build militia now. It’s going to take some time to get used to this. But no, you can’t just go and solo the monster layers anymore willy nilly.
Are you saying there's no more City Militia? That seems like a major change, and if so, there would need to be a ridiculous amount of re-balancing. Troops would have to cost much less (at least on the low end) and improvement would have to take less time - since you'll be spending more time making troops - and I already think improvements take too long to build.
Adventuring all willy-nilly is basically all the fun for me. I can't imagine playing this game and keeping my one Sov and the one "close to home" champ nearby all the time to defend from everything while the Wild-lands just sit there waiting for the end-game.
I guess I'll reserve judgement to see how it work with the new movement rules and bonuses in your territory, but this change sincerely make me feel like the pace of the game is going to be set to far too slow for my enjoyment. I don't want to take 3000 turns of micromanaging a half dozen to a dozen cities just to be able to go out to the Wild lands and get boot-stomped by a 500HP Boss.