The relevance weighting sounds like it would help. Do you think if a resource has the same title as a search query, it will show up at the top of the results?
How much extra work is it to maintain Elasticsearch? I don't mind doing extra work upfront to install it initially, but I'm worried about additional work in the long run.
Also, I have a suggestion. Xenforo should clarify the weaknesses of not having Enhanced Search. I didn't know that Xenforo only sorted search results by date, so that makes Enhanced Search sound a lot more appealing.