In layman's terms, more or less, the difference in cut/design, between an assy, & a standard kite, is like the difference between a dress designed to show cleavage up the mid-line, & one which has full "cups". So making such a change isn't the world's easiest task.
You realize that if a standard kite is long enough along the leech (either one), that you can fly it sans pole, with a tackline to the bow or a short sprit, & also a line or collar from that "clew", going around the headstay. ATN makes a product for the latter role/purpose, called the "Tacker".
You can check it out here, including a video of same, in use. ATN Sailing Equipment | The Tacker | No Boom Spinnaker Handler
Can't say that I've watched it, but perhaps it'll help you.
One Summer, 20yrs back, on vacation
I brought home a kite from my Searunner
(31') to play with on my Dad's Cal
29'. The shape & wind
angles, obviously weren't ideal. But given that we were doing 5kts in 4-6kts of breeze, he was EXCITED. And I was real happy that I'd brought it along, as even with his 150% up, we were just drifting.
was light the whole time I visited (and all summer) so bringing it was a good call. Especially as it was rediculously hot & humid, so the AWS helped a Lot with staying cool.
FYI, I just used some dacron through the anchor
roller, & back to a dock
cleat as a tackline. And a Wichard snap shackle around the wire headstay as a "Tacker".
If you look/pay attention, you can find used assy's. Or even approach someone who's boat's for sale
, that has more than one, & offer them some $. Especially racers with a rig that's the same size as yours +/-.
That, & sometimes sailmakers have sails
they made, which folks didn't pick up, etc.