I don’t know if this would be tenable or not, but often there is a most common choice for tuplet. Say if you have an 8th note, and you type 5 in the popover; to me this is most likely going to be an 8th-note quintuplet, spread over two beats.
And in jmatos’s example, a 16th-note sextuplet would be more common than 6:5, etc.
So if there were a way to code it, perhaps typing without a ratio could create a default tuplet (decided by the Dorico team, or maybe even in user preferences); and if you want something less common, you can always type the ratio.