Hello Mr. Carter, hope you are doing well.
Your Autocreation fails probably because the printers and or the drivers in your server's named differently and hence it fails. Good news is that you can avoid this as you rightly pointed out by 'overriding and substituting drivers on the server' i.e. by using the Remapping Feature: Which means we just have to eliminate faulty printer drivers and install fresh ones.
Now in the Citrix policy settings, from the "find printer driver menu", go ahead and select or add the driver that you want to replace for the printer driver.
After adding it to your mapped drivers, you would be able to edit it from the printer and compatibility mapping page, by selecting the specific driver you want to edit and then by selecting settings you could control color, scales, etc. That's it.