actually,
You don't have to go the DC route, a simple, standard reversing AC motor (like most US TLs have) will do just fine. There are many still being built and sold in just that form here in Europe today.
Nor is it all that hard to modify the belt tensioner to run in both directions. There are really only three changes necessary. The belt tensioner, the motor and the timer - you want a bit of a pause in there before the drum reverses.
But why bother? US dryers, unless horribly overloaded run just fine, their big drums prevent tangling pretty well. There is another reason. Many US dryers do have reversing motors...but when the motor is in "reverse" a slip-clutch on the motor shaft doesn't drive the drum belt. The blower and heat runs and with a simple rack, the dryer is optimal for drying sweaters and things which must not be tumbled.
I worry about the continuous heating elements in early Frigimores...got my folks one of the very last of the old series this winter and they use those horrid dryer sheets. No way to get anyone to believe me that they are dangerous. Anyone here have any good links showing the horrors these things can cause?