One-time Upsell Discount

After several false starts, I have finally figured out I want to sell my product/membership. The next questions is how to use s2member Pro/Auth.net to accomplish this.

I have a product that will be sold at Level 1 membership. I will use coupon codes to discount this product for launch period (large discount for taking fast action), then revert to original cost (on a specific date). I know how to do this.

I want to offer an upgrade to Level 2 Premier monthly membership. I know how to do the redirect for upgrade pages.

Not sure if I can offer a discount on ONE upgrade offer.

I want to offer a ONE-TIME upgrade at a discount on the monthly fee ($67) immediately upon purchase of the level 1 product. Then on future logins (periodically) offer upgrades to level 2 Premier monthly membership at the regular monthly fee ($97).

Is this possible with Authorize.net and Pro Forms?
If so, how do I offer the discounted monthly membership?
Do I use a coupon code, or can I program the one-time upgrade at $67 using Auth.net ProForms (with subsequent upgrade offers at $97 on a different Auth.net ProForm)?

I want to offer a ONE-TIME upgrade at a discount on the monthly fee ($67) immediately upon purchase of the level 1 product. Then on future logins (periodically) offer upgrades to level 2 Premier monthly membership at the regular monthly fee ($97).

Have you taken a look at this feature yet?
See: Dashboard -› s2Member® -› General Options -› One-Time Offers (Upon Login)
If you connect this to a URL that contains a Pro Form configured at a discounted rate, that should get the job done nicely. As far as the actual discount, this can come from the way you configure a particular Pro Form.