First: more power to you, and anyone else who tries to improvise.

My knowledge of suspension tuning is very slight. What I can offer is a prediction of how sanctioning bodies deal with innovation.

1. if you mail them a diagram and explanation and ask for a ruling, they will not give you legal status in writing
2. personal and phone conversations never took place, didn't go the way you said etc.
3. the tech line is only concerned with safety rules - not legality
4. being permitted to race doesn't mean that they agree that you're legal
5. nothing will happen until you beat someone important/influential - you know, the guys married to Force's cousin, blah
6. when protested you fail

The reason given may take various forms as to language, beginning by simply stating the "it's not in the rules" (actual non-compliance). Your objection that it's not prohibited will be met with "it violates the spirit of the rule" (translation: we don't like you).
The underlying reason is simple: you beat someone more important than you.
IMHO it's not legal, in that you're not using the suspension in a different way. It would fail an objection based on patentable engineering features (not enough commonality with OEM).
There are 2 main points of difference:
1. the original leaf was both the entire suspension and the locator for the axle, now it's not
2. a new part has assumed some of the original function, which is not stock