Instead of block rewards, miners will mostly rely on transaction fees.
This is when I believe we run into a problem. This is because historically humans have a strong distaste for fees especially with simple actions on the Internet. If we want Bitcoin to become a global currency that is used for primarily every transaction, having fees is an easy way to deter new people from adopting Bitcoin as their main currency.
Where this kind of assumptions come from? Did you make any bitcoin transaction ever?
Even now people pay transaction fees. Last 4 blocks came with 0.15, 0.08, 0.03 or 0.1 BTC for the miners from fees. When the network is more crowded, the fees increase greatly.
So.. one error in the logic is about the fees. People do pay fees already for the transactions and bitcoin didn't stop existing.
Even more, although you don't seem to know, but you also pay transaction fees in the fiat world, when you pay with your card. Just nobody cares to tell you that the merchant included that into the price you see for the product/service you buy and he's paying that fee to Visa/Mastercard (or keeps the difference if you pay with fiat).
Also, another problem I see is that the last halving will be around 2140. So you are trying to find the fix for a problem that might happen in more than 100 years. I think that too many things will change until then, hence it's too early for arguing about it.