In my opinion/experience... a 125 gal is good for 5 medium Cichlids... medium Cichlids meaning JD, Sev, GT or the like...
I personally love having breeding pairs in a community setting, but it is very difficult at best. I do not suggest anyone try this unless they have alternative tanks to move problemed fish to.
I think you should house the pair separate from the others...
I think a 125 gal w/ : Oscar, JD, Convict (you could do a pair), Chocolate & 2~3 Male (or 4~5 Female) W African Jewels...
Convict pairs are satisfied with very small territories compared to Dempseys or other CA’s... Convicts are the one fish I keep in community settings and rarely have a problem with...
W African Jewels are not CA or even SA... but they do live in the same water conditions naturally (W African Rivers as opposed to rift lakes). They stay smaller (4~5") but are aggressive for their size. I've been using them as dithers for my SA/CA Cichlids for a little over a year now and they have been working great. Breeding pairs can be quite aggressive though so I would avoid pairs in a community setting.
Using the divider is also a reasonable option, but divided display tanks are hard to make pretty… I’d assume that looks matter on this tank.
Whatever you decide on… it sounds like your on the right track and you also seem to be getting some balanced advice…