What is your throughput? Will you be printing in colour?
TNT labels probably 100 prints a day over 8 hours so nothing massive.
Why not get a dedicated label printer?
Get yourself two printers: one label, one paper. I've seen it when labels get wrapped around various laser printer innards and it's not fun and often expensive to fix.
OTOH you could just use normal paper and self-adhesive document pouches.
And think about getting two label printers - one as a hot spare. What is the business cost of not being able to label for a day or two?