clarity of the word "multipurposeness"

Multipurposeness is — in my opinion — an obscure word. It's likely to be unfamiliar to the reader, and you have to ask whether it adds enough clarity to the text to make it worthwhile for the reader to deal with the unfamiliar word.

Additionally, it looks like you've coined a nonce usage that only applies to your paper.¹ That means the reader has to reinstate the typical meaning of this obscure phrase, and then remember your unique adjustment to its meaning, every time they read it. That's a lot of work! Does it add enough clarity to make that effort worthwhile? That depends on the size of the text and how often the phrase is used. For a textbook where it's used throughout, and where the definition is easily accessible from the index, it's probably fine; for a short paper, I would be hesitant to use it.

¹ The normal meaning is, the quality of having multiple uses; what you mean in this case is, the quality of having two specific uses.

---

You could try replacing each use of the term multipurposeness with a short phrase describing it's meaning, perhaps using a different phrase each time. This might require rewording the sentence a bit to fit the phrase in.

Here's an example,

This technique achieves multipurposeness, ...

could be converted to,

This technique achieves both of our goals, ...