Many years ago when I was still “kind of” a kenpo guy I actually did this in a way.
The problem is, you are limited by your own experience and quite likely will have problems in what you develop. The system overall may not be very viable.
In my case, I took the Tracy curriculum, which is actually much larger than the other Parker kenpo lineages ( I prefer to refer to them as “lineages” rather than as “Ed Parker’s American Kenpo” because I think that reflects the truth a lot better, as the Tracy brothers were student of Parker in the early days, who split and established their own lineage, and the Parker Kenpo folks are also people who trained under Ed Parker at different times, and continue to teach what they learned) and made some serious modifications. I eliminated a lot of stuff that seemed repetitive and nearly identical to other stuff, eliminated a bunch of stuff that just seemed like bad and dysfunctional ideas (there are a lot of those, in my opinion) and re-wrote some that I felt had potential but needed to be tweaked. The result was kind of interesting, but overall I didn’t have a lot of faith in it as I was just doing it on my own, wasn’t training with anyone, didn’t have a group or teacher with whom to work it through.
Inventing a method on your own is difficult, you need to really experiment with that stuff to feel confident that it is sound and functional. That is actually my main disillusionment with the kenpo that I trained and the kenpo that I’ve seen: I feel that a lot of those self defense techniques are filled with bad ideas that would never work. The argument is that they aren’t meant to work directly, in a “problem/solution” sort of way. Rather, they are meant to give ideas of possibilities, and parts of different SD techs can be mixed and grafted together to fit a unique situation. While this is true in theory, I find it to be a very clumsy approach in organizing a curriculum, and the plethora of bad ideas just undermines the whole approach. For me, I finally decided that kenpo is not a good match and i need to do something else.