The fish you listed, will eventually fill up a 72x30 themselves if you account for breeding, which will inevitably happen. Rainbow cichlids will be too passive for this mix IMO. The firemouths like to live in groups of 5 or more, and to live with these other more aggressive species, I would recommend the group. The convict and salvini pairs will probaby fight. The best you can hope for is that the convicts and salvinis will pick breeding sites on opposite sides of the tank, and that the firemouths stay out of their way. Though it is a nice large tank, your starting point for the stock doesn't really leave room for much of anything else since there will potentially be 3 breeding pairs already, and there is high potential for things to go south as well. Though, if you pulled it off and had the three pairs all raising fry together, that would be a very impressive tank! Just my .02
If it were my tank, I would probably go for the firemouth group, forget the two other pairs, opting for some other single CA cichlids which would cohabit with the firemouths.. Perhaps oscura heterospila or, some fish from the astatheros genus. I think this would have better chances of working out long-term.
Edit: noticed after writing this that you put "couple male convicts" not just couple convicts. 2 male convicts would not be a good idea, one will bully the other. 3+ would be the way to go, or a single male which may be wiser and leave more room for other species. My advice is mostly about dealing with multiple breeding pairs in the tank, if you go for single convict and salvini (not pairs) and the group of FMs that would leave you open to more options. Ideas for species would be panamensis, centrarchus, astatheros robertsoni, maybe even parachromis loisellei with some luck. Getting all-males would be important because most of these fish will hybridize.