SLD starting with digit (or containing only digits)

Dear all, I would be grateful if someone could tell me what problems could arise by permitting domain names starting with a digit, or even containing *only* digits, under a TLD. I know this is not in accordance with RFC952. My question really is what technical problems could be expected if a TLD were to decide that it allows the above (and currently the required domain name length is only two characters). Thank you for any help on this. Janos Zsako