I completely agree with this suggestion.
iReal Pro is already very useful, but adding chord diagrams for fifths-tuned instruments would make it even more practical for many players. A CGDA chord dictionary, for example, could be useful not only for tenor banjo players, but also for mandolin, violin, bouzouki, and other related instruments.
Even better, it would be amazing if users could define the number of strings and the tuning themselves, and then let the app generate the chord shapes automatically. That way, it would not be limited to a few specific instruments, but could work for many different setups and playing styles.
This would be a very useful feature for a lot of musicians.