Can developers add maximum speed ranking in the Connect running activity interface?

I am not sure what exactly you mean by the maximum speed ranking. I assume you know that the maximum speed is already listed in the activity stats of Garmin Connect, so I suppose you either mean how your run ranked in comparison to your previous runs, or how it ranks globally (including the speed of other users). Such functionality would not be easy to add by a CIQ developer, since the CIQ API does not offer any access to your training history, hence the app would have to store its own history.

However, I'd tell, that there already is a better solution than a CIQ app for that - Segments. The Segments offer ranking of several types - personal, global (all users), between Connections, and in a Group. Myself, I use it in such way that I created short sprint Segments on the tracks that I use regularly, and then can easily follow the evolution of my max efforts on those segments.