How about implementing the possibility to define all routes in one place in a compact manner? In the Play framework, one sets out with
one line per route, resulting in a very compact and neat overview of all the routes in an application:
https://www.playframework.com/documentation/3.0.x/JavaRouting#The-routes-file-syntax
Having the possibility to define all routes of an app with this Play!-syntax in Ktor (or via Kotlin Routing) would be a very nice feature, both for me, who have been wanting it for a long time, and for others who might be tempted to migrate from Play! to Ktor.
(just my two pennies' worth.)