Helvetica Neue for small characters is just plain annoying to read on my 2013 non-retina iMac (while on my macbook retina I recon it looks good).
But just setting everything to Helvetica (with developer tools) improved the user experience a lot, as one can see on the attached files.
My suggestion:
1) enable users to set other fonts as default;
2) identify if the screen is retina or not, and automatically set fonts accordingly.
Thank you for the idea. Given the low volume of support for this idea, we do not have plans to make updates in this area at this time.