Let me explain about the concept of my project. They are two main searches:
Search1: As you can see the search on the home page, I want every word that maches a keyword to display. They are books. So, each post represents a book page. Category and tag are used for filter (category is the name for a book and tag is the name for the book types). Custom field is used to mark page numbers. In this case, the search doesn’t target category, tag and custom field, but mainly target contents and titles. But the titles don’t contain many texts like the contents. So, the search mainly targets the contents because they contain the most texts.
Search2: Mainly target custom field (I have some texts in the custom field to search for, it’s quite long texts), maybe target category, tag and other taxomomy terms as well.
Note: All the concept is to make sure that people get all the related search results from all the page from all the books. If what you suggest affects the search result concept, never mind I would prefer to go with it and choose a suitable hosting plan. But at least optimize what can be done if possible.