That's not a bad idea for a late-round pick or an expendable player, like Bell should they be hard up for Safeties (or way undersized LBs). He could compete with Bass and 'may the best man win' and the other be active as a versatile backup.
The thing is, Smith has been vehemently clear he doesn't want to move from Guard, nor do a lot of fans want him to move. But in my opinion, a good LT is more important than a great Guard, especially when you have other options at Guard who would probably be serviceable at worst.