Well the thing is that it would be easy that way to manipulate transaction fee charts in Ripple (since fees there are several orders of magnitude smaller than in PoW coins) and other similar coins and fees there do not necessarily represent the amount of "investedness" into the system. Transaction volume might be another indicator that looks nice at first, still it again can be easily gamed (I can afford to replicate every single transaction ever in all of Bitcoin into Ripple for XRP worth less than 20 USD in fees) in coins that have smaller fees.
That is why I'm saying: I'm not interested in doing something with the transaction volume, but would like to see the amount of money that people spend on transaction fees in total on using each system. You are talking about trying to manipulate daily growth of a single system, but that won't work if Bitcoin already collects $11.000 in fees daily, and you spend an extra 1 XRP ($0.028)