It's unclear why you think that you would be entitled to extra warranty or compensation for a product that is clearly beyond the warranty period.
Would you expect the same for your refrigerator or television that failed out of the warranty period? Or if you had a seven year old ICE that the transmission failed out of warranty?
The lesson learned here is to read the fine print of a warranty or any business contract, especially with extended warranties that are sold by retailers.
Nissan is absolutely correct that their dealers are independent owners, and that the way that they operate their business is something Nissan generally has no control of.
You say that you didn't pay attention to the terms of the manufacturer's warranty, nor did you take the time to understand the terms of the extended warranty, but you feel that somehow that the manufacturer and the retailer are liable for your actions. As the buyer of a product or service, it is your responsibility to understand the contract and the obligations of both the buyer and the seller.
Just think of this as a learning experience for you to pay better due diligence to what you are doing, especially when it comes to business transactions.
I wish you the best of luck with your next EV purchase or lease, but keep in mind that you will not be exempted from paying attention to the fine print just because you move to another brand or retailer. In fact you may have an even more unfavorable experience if you continue to not do your due diligence in the transaction.
Moving forward, since it appears that you purchased your LEAF rather than lease it, your options are to either replace the car's pack, sell the vehicle on the open market, trade it in for another vehicle, or keep the vehicle and live with its condition.
Nissan is willing to help you finance the replacement at most probably a favorable rate, which is helpful, but if your ability to afford that offer would be strained, that probably means that obtaining another vehicle might also be out of reach.
A used 2013/14/15 LEAF can be had for about $9-12K, and your vehicle is worth about $3K for trade, so that might be a better upgrade than just replacing the battery because at the end of the day you would still have a seven year old car but with a newer battery. A new battery would not change the fact that it will still be only worth $3-5K.
2018 LEAF SL
Delivery April 10 2018
2014 LEAF SV
Delivery May 23 2014
50,000+ miles - all 12 bars - Same range as new - No warranty issues ever!