From my experience there's only two cases where the "only the primary account holder" rule could burn you; 1 is if the other user you're letting use it is in a country we legally cannot do business with (in the past, this meant Iran thanks to the US sanctions on Iran; accounts with Iranian login history had to be suspended outright). I don't believe there's any restrictions on Italy with that regard, so that shouldn't be an issue.
2 would be if you let them access it and they do something against our Terms of Service (such as script hosting, bot, phishing, etc). I don't think that'd be an issue given what you're describing, but it's worth bearing in mind, since if they upload something bad, you're held responsible as the account owner. It's the same reason we recommend that users hosting forums on our free services moderate them appropriately - it's technically someone else posting the content, but it's the account owner held responsible.
In either case, you may want to jump up to x10Premium at some point; the only restrictions there are where it's not legal for us to do business (sanctions come to mind again, but there's none for the UK or Italy that I know of), but more importantly it'd be more stable with better uptime, which might not be a bad thing to have if it's a key tool/resource for your development team. We do pretty good uptime wise, but not as good as on premium
