All good points, I'm simply just experimenting to find a cheaper solution instead of having to buy new OEM ones.
Perhaps the bars are intentionally made weak for the reason to save the risers from breaking or damaged, it's far to say that removing this weak link, just moves the weak link to the next part.
But if you do happen to break or damage the risers, they are far more plentiful and cheaper, then the bars themselves.
An interesting observation I've made is that the PreGen Ninjette uses the same riser/bar set-up as other model Kawasakis, like the EX500, is a direct replacement.
I'm using a set of risers off a zx600 on my PreGen,
How to lower your bars.... as seen here in my write-up.
So it may be safe to assume that not only does the EX500 use the bar inserts, but maybe the ZX600 as well. I have no way to confirm or deny this, but it's a good possibility.
The bar stock I might use is carbon steel, or perhaps something else, cheaper, maybe just plain round bar.
As I said I'll be doing some experimenting over the coming weeks, right now I'm in the research phase.
So keep the ideas coming, and if anyone else is interested in an alternative replacement to the OEM ones.