That would require Proxying or "Counts as" but, myself personally and everyone that I have ever played with has no issue with proxying, so long as it's reasonable.
So long as it's clear which weapon the whole unit is using, nobody should have a problem.
However, once you start going to tournaments then it may become a problem as they have stricter rules regarding proxy and counts as.
Edit: Wording is very important. For example, if one word had changed it would be a lot different. If it instead had said "Some MODELS of Saurus Warriors wield..." Then, you would be able to mix and match their weapons. The same applies to the rest of the game, being aware of the difference between a Model and a Unit.