Dendarii
International Debutant
I think chances of it happening aren't that great, but throwing out another suggestion - Philander might not be the worst option. He hasn't played an ODI for almost three years, but he's got a good record (home is better, but away's still decent), so you could play Mulder at seven and Philander at eight. That's four frontline bowlers, Mulder/Duminy/Markram to make up the fifth, and reasonable batting down to eight.There's a balance problem no matter what. Too many bits and pieces options. 10 overs from these 3 is probably a better solution than weakening the batting to the extent playing someone like Morris does. With all the best bowlers being weak with the bat, it's probably better to take the hit on the batting side.
Fitness might be a concern, and he definitely wouldn't be long-term option beyond the World Cup. But there'll probably be a rebuilding process after that anyway, so just maybe worth considering.