Live print speed adjustments. For example, a person has been using a common setting profile, and they realize halfway up the part that it may have more vibration or ringing occurring than expected (what I just did). Instead of losing the rest of the print to poorer quality, or reprinting an entire print, an ability to forward a speed modifier across the live g-code stream could save someones day. To the contrary, if someone realized that they simply set a large print way too slow and they realized the print would be fine a bit faster, that could also save someones day--literally.
