It's not a bad idea OP, but it's just not a thing they want to happen. Most of the FFXIV collabs are, essentially, fancy advertising. They wanted FFXIV people to get interested in/buy Nier, or Dragon Quest, or whatever. Even the out-of-company collabs have mostly been about cross-pollinating to attract business from other companies.

So, unless it is still a newish game or getting sales, I wouldn't expect it. In fact, I'd expect your next major collab event to be with FFXVI in 2022.