Ive never been a fan of cross systems and I hated FFXI's version and the expectations it created. I didnt play much of XIV when it had it but I think I ignored it entirely.

In FFXI I just rejected others opinions. I ran THF/RNG and WHM/BLM because I dont like SMN and I found Wide Scan more useful for things I was doing. Those were weak decisions despite being more fun.

Cross class is interesting on paper, and fun to think about, but when you add a gaming community to the mix they just suck all the fun right out because anything that's not minmax is "wrong". Itd be neat if it worked though.