Its supposedly possible to have a more than 4 companions mod.

This screenshot being from 5 years ago seems to have claimed to be able to remove the party limit using the 5th dog slot as a code source. Now obviously this would be very cool albeit game-breaking, but it would be very cool to hear all the dialogue.

But unfortunately, there's little chance the person is still working on this, as i have messaged them myself and never got a response. It would be very cool for someone else to try their hand at making this and release it.

https://www.nexusmods.com/dragonage/images/51197