If the? games are going forward in time...
Thy should make an appearence of basic guns.
Flintlocks...wheellocks...gren-ada... also you should be able to sail.

These are some of my ideas. I just think you should be able to sail boats and do some other things.
To actually move furniture in houses to where you want. camp sites possibly. and gangs.

Why would you need a gun when you can cast magic? This game is set in the second era while Skyrim is set in the fourth era.

They aren't. The Elder Scrolls Online takes place 1000 years before Skyrim.

This.

And no.