I don't know, John Bell might have been OK.
In a calmer time, Bell could have been a good president. But as far as age and health, he might have been past his prime by 1860. I've read some from contemporary Tennessee histories of the period, and during the Tennessee secession crisis Bell proved indecisive and vacillating. Had he won the 1860 election he might have continued the Buchanan policy of limbo and chaos.