I formed a single person LLC, but I've realized I should have formed it under my wife as she will be main person operating.I was about to start the process to file an amendment to remove myself from the articles of organization and add her as the sole member.But I read in Florida there are cases where the corporate veil can be pierced. 

You could amend and claim refunds of erroneous prior taxes paid but if you filed with the intention of misleading your lender you are likely committing mortgage fraud. 

Amend the lease, raise the rent.

Can I convert after purchasing  amendment to the lease and change it to NNN lease?

If you're willing to give them an extension make sure you amend the contract and put the new date in writing. 

Here's the "special rule"https://constitution.laws.com/american-history/constitution/constitutional-amendments/27th-amendment

For those not familiar, the proposed Fair Tax legislation calls for full repeal of all forms of Federal taxes except for the excise tax, replacement of those taxes with a consumption tax, and repeal of the 16th Amendment within 5 years of the Fair Tax passage.

But if you were looking to just put the property that you are buying into a LLC that you own then a contract amendment is all that is needed. 

@Jack YoungThe "new" lending criteria in the latest amendments to B-20 are really not "new" so much as a return to the practices of an earlier time.Given the band of interest rates for real estate financing in this country is historically in the 6-9% range, you should be using criteria at lease as rigorous as the new stress test when analysing a potential acquisition. 

If you need days, try to get an amendment to the contract.