All you have to do is just copy-paste the original Citroen DS shape and just make it look more modern through the details and fittings.
This attempt from back in 2011, while described by the unflattering previous sentence, is still quite nice to look at and contemplate and probably one of the best attempts at this arduous task.
The original source for this rendering is this old Tumblr account called Citroenbuzz, but we’re not really sure it originates there – that’s just where we found it.
As for the design, there really isn’t much to be said here. You look at it, examine it for a few seconds, then make up your mind if the shape is pleasing or not – I think it is, especially envisioned as a coupe.
Citroen has never actually attempted to revive the old DS, and I think that’s because it kind of knew it was going to get it wrong somehow and people would boo. Yes, it would have been brilliant if they’d pulled it off, but it would have been disastrous for their image had it gone wrong.