I recently had a problem: during navigation, I got a warning message on the screen, saying that my internal storage space is full, and offered me to delete some apps from the phone. Take care: I am not speaking about RAM, but internal SD-card.
Actually, my phone has a 500 MB internal SD-card, and it was quickly depleted.
I did previously install Link2SD, and practically all my apps are on the external SD-card, but the data are still stored on the internal one, this is something particular to Android, users cannot change it.
My solution for this problem would be to make waze in such a way as to save on-line map data piece by piece, then delete the older ones if the internal storage gets low. In this way waze would never consume more than enough internal storage room. Could you please pass this to the developers?