Any evidence to support this assumption?
It's not an assumption, it's the result of thinking and reasoning.
Also if you think bitcoin needs to be modified you're the one that has to construct a valid point.
Doesn't the data already indicate that most people pay the minimum Tx fee despite most blocks being unfilled? (They have a choice of paying nothing and waiting a couple days)
That's because most clients force it on them.
Doesn't the data reflect that Tx fees are starting to cover the costs to secure the network
Lol no, compare the tx fees to the current block rewards.
Where is your evidence to suggest otherwise?
T'is in the blockchain baby.
Why would you assume people would pay 40 cents per tx fee with a full block vs 4 cents with an half empty block?
Because people aren't even paying 4 cents today.
You just contradicted yourself. First, you agreed with me that most are paying the Tx fee because it is forced on them by the client, than you are suggesting most aren't paying them today? (I'm going to assume you are being reasonable and not arguing against 4 pennies because the drop in BTC value, as a 2-3 penny Tx fee would equally apply to my argument)
Even if clients didn't have a default Tx set (which can be removed in many instances) they do this as a convenience to clients because the users would be pissed at having their transactions taking days to accomplish and promptly add the Tx back themselves.
I have provided some evidence to the table and still have yet to hear your evidence rather than vague allusions.
Answer this question please which you keep avoiding:
4,000 transactions per block @ 40 pennies each(Full 1MB) vs 40,000 transactions per block @ 4 pennies each(half 20MB) = 20MB block equally secure or Insecure?