is this for use against ai and players?
in that case it would be a detriment (hehe) to your skill as a player.
as the battle progresses the units you will need are very different from moment to moment, limiting yourself to 5 thugs and 5 roughes at all times (example) is likely going to cause you to lose most fights. it is predictable, inflexible and inefficient.
you could argue that you can change the units and amounts you want, but this you can do by looking at the battlefield and building the units you need in that moment.
going back to configure a widget everytime you need diffrent army compositions sounds like a wonderbard apm sink, you should learn to make use of the factory hotkeys and stay ahead of the opponents army in couter ability
basicaly you re cutting on the time it takes to queue an army (seconds?) and adding to the time it takes to respond to your opponents army, which is quite often already taking too long (acquiring intel, building counter, moving into place, striking)

yours truly the dream catcher

Even if you don't wanna handle your whole army management to such a system, it could be useful in a lot of edge cases, such as always having a small force of scouts/raiders ready to go, automatically replacing constructors who got toasted in the frontlines, and other specialist units you need in small numbers.

There's a page on the zero-k wiki entitled 'Widget Configuration' which starts off with, "This is a page is intended to be filled with some commonly asked about configuration questions which can be solved with relatively simple changes in the non-advanced menu." I can't find a link to anywhere else on the zk wiki explaining widgets. I've edited the wiki a touch, adding some steps to make widgets work. Is it good?

(Widgets now also redirects to Widget Configuration.) I know that there are online repositories of widgets, but I don't remember where they are, do you think it would be good to add links to them accesable from here?