Is there not a recommended install procedure, spec sheet etc available from the manufacturer? Usually there is a least a list of acceptable substrates. That would be a good place to start, because ‘brick veneer’ could describe a variety of products with quite different installation requirements.
I always research product I am installing even if I am hiring a sub trade to install it. A lot of guys just do what they’ve been taught or think is good enough or can get away with. Coming back to fix shortcuts is just too much of a hassle, so I rather it be done right, and manufacturers recommendations are a good start.
Its pretty easy to cut out drywall and replace it with whatever is best. If just using thinset adhesive Hardi board, Denshield or cement board are better substrates than ordinary drywall. Tile is often installed directly on (sealed) drywall in dry locations, but brick veneer may be a bit heavy. If metal lathe and mortar are involved plywood is going to be much nicer to staple the lathe to rather than trying to staple through drywall to studs. I cant imagine Hardie board is good to staple into.