I think you're over complicating things but that's just my opinion. Also seems like you'd put in a lot of time just getting a flow chart (?) correct, only to find when you build the form it doesn't do what you thought it would. That makes the plan document obsolete? However, it's not an opinion to say that a textbox has no rowsource property and an optiongroup has no OnChange event so not sure what effect such errors could have on the plan. In those two cases, probably nothing as there are alternatives.
To each their own, I guess but I would not spend the time to create such charts.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.