Your idea is pure genious! The howls and roars need to sound different, people would then actually sometimes, in a wolf rp for example, have a group howl that wouldnt be the repeating of the same howl over and over again. Same for the lions, I imagine teh leader to have a really strong roar and be like simba at the end of the first Lion King movie...xD Also, for those that rp as dragons they'd have a really strong howl or roar, instead of sounding like a normal animal.