Technically since the Frontosa are bottom dwellers and the butterflys are top dwellers the two would mix without much difficulty. The only problem I see is that Frontosa should have hard, alkaline water and the butterflys soft, acidic water, if you want to see the best of them, though a PH of about 8 will suffice for both. The Pictus should do fine as well since they're also nocturnal, but make sure to provide little caves for them that the Frontosa can't get at.
Just be careful how many fish you stock, unless it has 48"x24" dimensions, a 4 foot tank is really small for a Frontosa harem and you'll want to be careful about water quality as they grow - they do need it pristine, like most Tanganyikans.
