Create a Wordpress plug-in

I have a WordPress website that uses a custom plug-in. I need a modified version of that plug-in, while keeping the original version in tact, so that I have choice of using one or the other. The current plug-in shows all of the available Google fonts in a drop-down list, and a color picker that looks at three different pieces of text and allows the user to change the fonts and color of that text. The user's choices are then recorded on a form which is emailed back to me. Because there are over six hundred fonts it takes too long to load. I want to put a list of one hundred (approximately) fonts that I will select that will show up in the drop-down list in the font of their name. So that a "New Times Roman" option will show up in the new times roman font, the "Comic Sans" option will show up in the comic sans font, and so on. The site is live so the work must be done on a copy of the site or in a manner that will not affect the original site until it is finished and approved. This should not be a major re-write and I will supply the names of the Google fonts to be used. I do need to get started fairly soon. The current page can be seen at [login to view URL] the end result will look the same, just the drop-down list of fonts will be shorter (and faster).