Gasly to Alpine and Ricciardo to AT does not seem like a weird scenario to me. Gasly has been tried and tested, and his performances are decent to good, but not standing out. Plus the upward trend has stalled. And he is not the most marketable personality(to an energy drink company). But he is french, which I think Alpine values.
A Ricciardo performing at his normal level should be able too perform a similar role at AT, while being more marketable. And if he finds back the good version of himself, he may be more than that.