Customize slug by passed arguments

How do you change URL based on passed argument using only one template?

mysite.com/regions/regionA
mysite.com/regions/regionB

(Region A and B are the arguments being passed).

Scenario :

1. Custom post type are loading on front page

2. Some of them are sticky and need a custom permalink based on an attribute (here it’s the region). I change their links and point it to the regions template.

3. Condition (if/else on query related to regions) and passing region’s name as an arg using add query arg

Unfortunately the link is ugly. How would you change that? Thank you!