A compromise could be to have some simple icons available, either as interim until the larger icons are available, or as a supplement.
In addition to "small" and "large", there could be an option "large text", which has simple but readable icons, each having 1 or 2 letters on them to indicate the usage of that button. I'm assuming that designing an Icon containing just a text letter would be much easier than scaling an image to the appropriate size.
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