Oddly - I hate cruising but When I was teaching, loads of my college students had great times working on board, but rules can be amazingly strict on any subject, let alone anything they may consider safety linked. Since then I’ve been on ships doing rigging and as visiting bands, and P&O, for instance would not allow us our walkie-talkies, because they did not have time or inclination to investigate and test them, so just handed us some of theirs - so it’s not really radios they don’t like, but what they could be used for. So many come with frequencies totally banned. Yesterday a new VHF radio arrived and when I downloaded the radio, it was programmed with marine band channels - I had not asked for this, but they were not the real marine frequencies, which use a mix of simplex and semi-duplex - just 25KHz channels starting at 156.000 (An emergency coastguard channel not available to the public here) and going upwards for 128 channels! Anyone buying these could cause serious problems and because they were set for simplex, they might be totally unaware as they’d not hear the coastal stations using them. This is why they hate random radios. The RT1 is a decent radio but just because it can be programmed for a set of channels, in some jurisdictions this is still risky, approvals wise. You also need to keep in mind the people you speak to at the cruise line won’t be technical, and are very unlikely to pass your request on.
For what it is worth, I’m aware that lots of the groups of workers (mine were the singers, dancers and technicians) use zello on their phones, using the ships internet. Data usage is minimal, and they set up big groups, so the friends can all hear each other. Using a phone also makes them inconspicuous, and as there are nodes everywhere, they work in cabins and anywhere. Radios are actually rubbish - radio to radio, as everywhere is metal compartments that are very range unfriendly.