I really think it takes more than a facial resemblance, I would expect them the have a similar height and body-shape, I would be looking for the long skinny arms...to start with.
Or else we end up with something like the Frank Marshall Davis idea, and he was a dumpy little fellow with no chin: 
I don’t know Fred... you are talking a farm laborer/village and garden-self reliant live off the land guy compared to a puny, lush Hawaiian ‘intellectual.’ Hard work will give arms depth where non-work will leave them scrawny.
Obama in black shorts, a bit of a middle age belly, and dark skin vs. Obama in almost too revealing red shorts, buff body, and light skin. Naw, there's no photoshopping going on.