A UV or skylight filter rather sharply take out UV and upper blue. Even light blue like Y2 will take out the above and a lot of green.
Unless you are mainly shooting ortho for ease of handling in the dark room, then it kind of defies the purpose of a fast ortho film.
A green filter on normal film will look much the same.
When you want good skies with ortho, taking out UV is important, but generally controlling exposure of the much brighter sky is also important.
Pol filters and gradated filters seems more effective to me, while keeping the character of the film.
For sky, your idea is probably very effective. But the point of the K filters was also general contrast, which photographers always have used at least a Med Y filter both for orthochromatic and panchromatic film. When I am shooting fast film, I will use Med Y until the light stops dropping a lot, at which point I just take it off, but that is me. I have gotten great shots without it, and others just don't use it. The effect in the end is subtle and does come at a price in speed, but I feel I prefer to have the medY filter if prevailing light and film speed support using it.
Good modern panchromatic films (such as Ilford and Kodak, as well as some others) have a pretty flat spectral response across colors. The eye does not, and you can end up with little distinguishing between colors. Of course it is also good to consider what the colors are, and in some cases pick a different filter color to exploit. Just a simple example- this picture had small yellow flowers in the grass. I used MedY, and it helped to distinguish them a bit. It was FP4+, so I suspect it would have been fine without the MedY, but with MedY it gave just that extra zing. The grass may have had some blue in it, because it looks dark. If I were using Hp5+ for instance (generally less contrasty than FP4+), and no filter, the flowers may have looked light, the grass lighter also, but the flowers may have blended in more to the grass, not sure.
Generally, I like the way various vegetation turns out with FP4+, which I always shoot with MedY. I must admit I have not done testing without MedY, but I strongly suspect the MedY does help.
Bucklin scene 2 by
Mark Wyatt, on Flickr