The VersaMil kit (look it up) included a tiny short-throw shaper attachment, ideal for things like spur gears and keyways. The basic "Mil" attaches to the compound of a reasonably stout lathe, so it might be an option if one little shop doesn't have much space.
I was aware of the VersaMil products, and you are correct they are small. Small enough they fit in cramped quarters like submarines. I know Brian, who appears to own VersaMil, posts here on these forums periodically. I know there are pictures of that shaper attachment in other forums dismantled. I also know that the kit is quite expensive (though comparatively $450+ for a cast steady rest on a 12" lathe with less driven pieces is not cheap either) with some parts on eBay right now upwards of several thousands. Finally the stroke of that attachment is about 4 inches and it appears many, not sure how many, are pull shapers instead of push.
I know the Navy used these VersaMils during training on lathes to cut gears, but South Bend had a gear cutting system and so did Atlas (appears to be a plan that used the lathe milling attachment to hold a finished gear to make an indexer on one side and the blank on the other with the gear cutter on a shaft driven by the lathe head and supported by the lathe tail stock).
My CNC gear cutting setup is basically also supporting the cutter between the lathe head and tailstock. Except I have a 60:1 worm gear module driven by a 0.9 degree stepper and the shaft for the blank is supported by a center opposite the driven end. For reference a Sherline rotary table is a 72:1 reduction with a 0.9 degree stepper per their documents. I also made a coupler behind the gear assembly turning the blank that accepts a high resolution encoder so if you use microstepping you can turn that gear blank nearly thousandths of a degree. As everything is fully supported end to end (unlike I have done on vertical mills) I get less deflections during operation. I can also cut helical gears with this setup by tilting the blank holding module on the lathe cross slide. So I wouldn't get much from owning a VersaMil for gear cutting, in fact I can already do the gear cutting on my one small lathe under CNC control while I turn the blanks on the other. Obviously a shaper can cut gears and even toothed pulley profiles, but the gear cutter is cheap enough I couldn't justify the cost of a shaper for this unless the profile was hard to source a cutter for.
I can certainly benefit from a shaper for keyways inside of gear blanks. I do this with push broaches on a 5 ton arbor press currently. I've got a rotary broach as well. The big issue I have is the all or nothing aspect of the push broaching process and the cost of these larger push broaches adds up. I'd rather let a shaper cut away in repeated strokes in some cases than have the push broach wander and cost me a gear.
Size is definitely not stopping me from considering the VersaMil, but rarity and cost would concern me. These systems command high costs even on the used market. That being said, as small and simple as the VersaMil shaper is, it still gives me pause 'how much shaper' I really need.