This is a good idea, though (for reasons Altenbach cited) it would likely be implemented like this:
Without this modification, it is hard for me to see how useful this dialog is -- would make a reasonably good solution for making an Options dialog if you could supply a current value!
As an easy workaround ... there's an easy fix!!! Build the dialog you want. Then right click on it and choose "Open Front Panel" and click "Convert" when asked. In the panel that appears, you'll see the controls on the front panel that are the default values of your inputs. Simply connect those inputs to the connector pane of the subVI, and now you have your default value inputs. (Also delete the "Reinit All" node on the block diagram.)
I think you should ask technical questions over in the LabVIEW forum. The ideas exchange is not well suited for this, for example we cannot attach code to replies.
Any idea that has received less than 2 kudos within 2 years after posting will be automatically declined.