As far as I understand your principle, you propose to regulate the transaction fee through changing the block size.
I suggest another option: adjust the block size by changing the transaction fee.
Let's say we have a sample computer of the lower segment, and we focus on it when setting constraints.
We can count the parameter:
1. The maximum block size that our sample computer can process in the time we need.
Additionally, we can evaluate one more parameter:
2. We estimate the maximum level of growth of bitcoin, based on the level of technology development that we can afford.
Based on it, we calculate the parameter: average block size.
The main idea is really not bad but I think we'd have a hard time to get everyone to agree on those terms... As you suggested, there would be a strong correlation between the min fee and the amount of transactions that is being processed by the network. We could consider the variation in the amount of transactions from one block to another one to calculate the min fee on the next one. The min fees would then determine the size of the blockchain on the long term so we could rise the block size limit 10x (or even more) and it shouldn't cause any problem. For now we would just need to all agree on the same formula to calculate those min fees...