I know what appealed to me on the prior subscription was the discount for 6 and 12 months . . . . that and the one time offer for an extra % off.

So perhaps instead of a grandfathered rate, have some "Welcome back" discount code.

Also, since there could be future ala carte "add ons" limiting them from other subscriptions (aside from the basic) is not a good idea.

Like I did before, I'd be willing to invest and see for 6 month periods and see what unfolds.