What an incredible range of wise, insightful replies. Thank you to each and every one of you. It's interesting, we seem to be divided into two camps:
1) Those who want every single garment to work HARD.
2) Those who will make room for garments with limited usefulness.
I know being in the first camp would make ones wardrobe more functional. However at the moment I think I am in category 2. Although this cardi does none of the work I expected it to when I bought it, I do especially like it as a completer piece for the voile top. Because I love that top and don't have many toppers for it, I am willing to allow this cardi a bit more leniency than it deserves on its own merit. People's suggestion of changing the buttons makes great sense, however I think the tightness of sleeve, and mediocre quality of the piece precludes it from having any money spent on it. If it were a higher natural fibre content I would be willing to spend on altering buttons.
I will try the following excellent suggestions:
1) Using it buttoned up as a top in itself.
2) Testing it with the other sleeveless blouse I have that I think may work with it.
3) Stretching it out a little next time its wet ('Sizing/blocking' the knit).
....and my own two ideas:
1) wearing it open over a white cami with a statement necklace.
2) Trying it over my two sleeveless dresses... just in case.
Thanks everyone, you have really helped me out with my thought process, and the insights will be applicable to other wardrobe dilemmas.