Router is designed for SEO, so yes you can do that.
Then, it is customizable in
Function : XxxxRouteConfig()
(Available since 3.1.3)
I see, you do do have even title is this table, so you might hit a foreign table.
Router is using ORM, so in the 'aliasKey', just define the namespace you want.
Here an example :
'city' => array(
array(
'type' => 'layout'
),
array(
'type' => 'slug',
'aliasKey' => 'country.alias' // HERE the namespace for the slug
)
),
I didn't tested, but it should work. Tell me, and share your result...
Note that this will take the FIRST result only, so it might work only for 1:1. In case only the first result will be used.