Add-on [Paid Job] InfusionSoft integration, allow users to opt-into newsletter upon registration

I am hoping that I can have it so that only contacts who check an opt-in box (with double email confirmation) would be synced to my InfusionSoft account. Is this possible with modification of the following addon: Infusionsoft API by Waindigo. Otherwise something 100% custom would be great.

I want users who don't want to be subscribed to my newsletter to only get xenForo system emails, but for people who opt-in to a newsletter to be added as a contact to my InfusionSoft account.

I hope this question makes sense.

User registers and doesn't click checkbox that they want to opt-in to newsletter -> never gets added to infusionsoft
User registers and doesn't opt in -> goes to profile and opts-in at a later date - gets added to infusionsoft
User registers and clicks checkbox that they want to get newsletter -> gets added to infusionsoft

To be clear, I'd want an opt-in area (with a checkbox and description of the newsletter) to be on the registration page.

Along with that, I would like for an opt-in area to be in their user settings area, like as seen in this outdated addon:

Looking for custom development to make this happen. Not sure if you can somehow modify / work with the Waindigo Infusionsoft API, but either way I would like to get this accomplished within a month or two. Please reach out to me via PM with a cost estimate (or post here to connect).

Thanks for your time, developers.