"Transform" existing font to variable font

@m4rc1e, @RosaWagner: A bit OT, but how hard would it be to transform an existing font, e.g. Arial or a very Arial-similar font to a variable font? I want to stretch the letters of an existing font. Currently, I have to use CSS transforms, but it interferes with the layout in the page. Having an axis for stretching the letters would be great. Are there Arial-like fonts or conversion tools for this?

So this boils down to this: Font should be stretched in width, no extra typographic adjustments, just heretic font stretching.
This is currently achieved using CSS transforms, which got many side effects.
Can an existing non-variable font be converted so it can be just stretched evenly on its X-Axis?