PS.
As with many open-source projects with some reach, there's no shortage of commercial products and options that will allow you to do exactly what you're asking for.
For example, it can be seen that ASIPTO put out a Kamailio-based load balancing solution:
https://www.asipto.com/sw/solutions/
And likewise, there are many other companies involved in the Kamailio space that either have a finished load-balancer built on top of Kamailio, or can provide you with one on a consulting basis:
https://www.kamailio.org/w/business-directory/
My initial response - that you were being presumptuous - was to your coming in here and telling everyone what the project is and how it should work. :-) I am telling you, in so many words, that the project is what it is, and probably doesn't have the same use-cases in mind as you do.
-- Alex