Top dwellers like danios make superior tankmates to tetra's because the naturally stick near the top. Since severums are a mid dwelling cichlid, it's safest to avoid small or skittish mid dwellers. The danio's will most likely be ignored - because of their speed and activity, their place in the tank, and higher numbers so none are targeted, the sev won't see them as food.
I've never tried it, but I absolutely would if I wanted sevs. Remember, these sevs are young and the danios wouldn't even make them look twice. By the time they grow they'll be used to the danios company and will most likely continue to ignore them. In a few years when the sevs really get large, they can always be replaced with giant danios (or even better, you can use giant danios from the start). I'd also add some medium sized catfish or loaches.