Nav V5: Lot numbers - lot number character input limits

We are receiving e-cert products that we input into lot number field. The Navision limit is 20 characters but we actually need up to 25 characters. Our support company has advised that trying to extend the lot characters is a major exercise and affects core inventory processing functionality, so any changes will be a major risk. Has anyone else looked into this situation or found other solutions to resolve ?

Thanks

Mike