Easy enough to include a barcode if there is a format that can be agreed, there's a zillion different formats out there. But as you say, all that is doing is replacing a 5-digit number which is no big deal for someone to key in. A barcode that is both event-specific and rider-specific is a more powerful tool, but much more difficult to arrange.
Personally I would just click people through using a live Start List on a smartphone - the main difficulty with that is restricting access to the list to the appropriate helpers.