I added home row mods (and compose) to my keyboard using Kanata, and I also added mouse movement.

Compose is on capslock tap, capslock is on capslock hold, tab tap is tab, tab hold is escape, homerow is as follows: lmeta, lalt, lshift, lctrl, ralt, none, rctrl, rshift, ralt, rmeta. Yes, there is a rmeta key on the azerty G, because it is used a bunch in Bépo.

About mouse movements (going off the prints of my azerty keyboard):
hjkl: Vim movements
yuiop: left, center, right, mouse4 and mouse5
w: scroll up
x: scroll down

Those keys are bound to hardware keycodes, and the remapping happens before layout applies. So there are no problems using it with Sway layout management, as long as the input keys are the same as the output keys. Any other mapping might not create the output you expect, especially with very changing layouts like Azerty and Bépo.