Thanks for the response.
The dice roll system will keep the combat interesting.
The settlers model will work like this. When you build a stone mine or wood camp or a farm, the building will initially create x number of workers. Then if you want to increase production, you can upgrade the building and extra workers will appear and start working at the place. You can upgrade the building a third time and a few more workers will be provided. This way you only need to manage the buildings and not individual workers. Also, since the player controls when to upgrade, the game will not waste the resources you need to create military units.
On the model detail, people like to zoom in during battles, and many RTS games provide the choice of zooming in up close. I would like this game to give players that choice.