Change uploads folder location with multisite and domain mapping

Hey y’all,

Our website loads relatively slow, and I’ve read that load times can be improved significantly by moving the wp-content/uploads folder to a sub-domain. Problem is, I’ve got Multisite installed with sub-directories, and a complex web of domain mapping setup so that democracyinpractice.org (our site in English) and democraciaenpractica.org (our site in Spanish) are both hosted on the one Spanish domain (the English domain is technically at democraciaenpractica.org/en although this never shows). So, given my limited knowledge/experience I don’t want to try switching over to sub-domains at this point.

Can I get the same fast load effect if I move the wp-content/uploads/site/2 folder (that corresponds to the English site) to the Spanish domain (democraciaenpractica.org/uploads), and the wp-content/uploads folder (that corresponds to the Spanish site) to the English domain (democracyinpractice.org/uploads)? Thus when someone visits the English domain media loads from what looks like a separate Spanish domain and vise versa for the Spanish site?

If this would have the same effect on page load times, I’ve seen a few different recommendations for how to move said file – what would be the best way to move it permanently so that all future uploads automatically go to the new locations?

Many thanks in advance!
Adam