Given the circumstances as you describe them, I don't see "doing nothing" as a realistic option.
Clearly this was an operating lease. You are fortunate with the timing since all years can be amended.
Option # 1 - Amend all years
Option # 2 - File a 3115 - Change in Accounting Method
In both scenarios you would reverse the previous entries and expense the operating lease payments, then allocate the 70 K residual payment to the assets and capitalize or expense accordingly. The choice between option # 1 or option # 2 would depend on the effect of each years taxes and on whether the 3115 calculations would result in additional tax due or not. If the 3115 resulted in additional taxes then you would get a 4 year spread on the payment.
It will be very interesting to see how this turns out. Keep us up to date !