One difference with the Monero model is that the amount of the fee is not a factor of the penalty, nor is size of the coinbase reward. The penalty is not multiplied by the block reward. Additive, not multiplicative.
I'd missed that detail at first pass because it seemed impossible for anyone to advocate such a function, when on its face it seems to fail the 'future-proof' test.
Without knowing what the fees will be in the future, how can the penalty be the same for every transaction? Fee amount tends to adjust with how much milk and bread a bitcoin can purchase. The penalty may thus become overly burdensome (if bitcoin value increases) or meaningless (if it falls).
We can know the coinbase reward, but we should not always expect that to be 99% of the total as it is now. This will matter later.
The advantage of the Monero multiplicative method is that it does not have to guess, it works at all fee levels, block rewards, valuation, etc.
As I've explained multiple times, this is exactly the reason for choosing a hyperbolic function. The marginal penalty is the derivative of f, f'. f' ranges from 0 to infinity when the block size ranges from T to 2T. Whatever the current Bitcoin price etc., there is some x for which f'(x) is equal to the typical fee. So the block sizes stretch and expand to accommodate the changing fees.
The same happens with the quadratic function in Monero, but much more slowly, giving us less control over the block sizes. Because of this, the quadratic function actually assumes more about the fees than the hyperbolic one.
The penalty itself (as opposed to its derivative) is less important in my proposal, because it more or less cancels out with the collection from penalties of past blocks. But still, we prefer to keep the penalty as low as possible, meaning that we are interested in the ratio f'/f. A hyperbolic function, because it grows faster, achieves a better ratio - and we can improve it further with parameter choice.
Furthermore, if the reward is (1 - penalty) * (minted coins) + tx fees, then in the future when the minted coins go down to 0, there is no penalty at all. That's the opposite of future-proof.