In my experience Severums are far more aggressive than Angels and much more robust. It could work if you get a very placid Severum, but i don't think i would do it.
I keep my Severum with an Oscar, JD, Salvini and Blue Acara. Basically, same size and slightly on the placid side or smaller and more aggressive. I would class Angels as peaceful in comparison to most cichlids.
I keep my Angel with a Discus and a little collection of rams in slightly warmer water (although that's less so for the Angel and more for the others).
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