Regarding the 310 vs. 58 Baron, I'd agree that the 310 is a more fragile airplane than the Baron. As far as maintenance costs, I have no idea on comparison since I've never operated a Baron, but I'd expect the two to end up costing similar per hour since they have similar engines and props. Thus your fuel burn and big maintenance reserves will be the same. The Baron is a bit faster on the same fuel burn.
The catch for me is that the Baron's cabin feels significantly more cramped than the 310's, and I also find the 310 to have significantly better forward visibility. To me, it's an overall nicer flying experience. So, even though I'd agree the 310 isn't built as well, I'd prefer one anyway.
Of course, Morne doesn't want a 310 or a Baron, he's looking for something that's more unusual and somewhat of a red-headed stepchild. So, a Twin Bo or a 337 should fit the job. The only Twin Bo owner I ever talked to had one with the straight GO-480s, and he said he loved the plane. It flew well, it was quiet, and he found it to be pretty reliable for his pleasure flying. Clearly he'd not been hit with a big engine bill.
If Morne could trade a bit of lust for the impractical in favor of something that is more practical, then perhaps an early model 310 would be a balance of impracticality with functionality.