It’s very common to change types and diameters where there’s a need. Thin and short sections around rotators, or through holes, but the issue is always the connector loss. The best connectors have some, cheap ones have less. You just do the maths. Add up loss end to end with lots of versions, and use the most appropriate. Sometimes the expensive low loss cable plus connectors is no better than one length of less good and probably cheaper cable.
On commercial masts really thick cable goes up the tower, but thinner stuff connects to antennas and equipment at both ends.