No I would not.
I would make the fire mouths the only cichlid species in the tank for three reasons.
Firstly you will have problems with aggressive behaviour. If you go for a group of fire mouths the convicts will not have a large enough territory of their own. Convicts can be very aggressive if they don’t have a large enough area to call their own and they would easily over power a fire mouth.
Secondly convicts and fire mouths can cross breed which is something I would discourage.
The last reason is,a tank full of fire mouths on their own in the right set up is a lovely sight. Done properly you can create a stunning display and witness fascinating behaviour. They are some of the most interesting fish I have kept. Their manageable size and aggression level make them a gray long term project.