1) Given that actual -non-maintenance- capex on the networks of the major ISPs appears to have been practically zero for decades, I suspect that the major ISPs will claim (and have the paperwork -however legitimate- [0] to back it up) that their per-customer profits are near-zero or negative.
2) Good ISPs are run like good utilities: any actual profits are either invested in the network, or returned to customers in one way or another. [1] This means that good ISPs actually have a near-zero per-customer profit.
So, all you're going to do with this plan is:
* Raise the -already high- barrier to entry for independent ISPs.
* Make a lot of paperwork.
* Make a lot of DPI hardware vendors very happy.
Noone will get more money, except for the DPI folks. :)
[0] Hollywood Accounting, anyone?
[1] Either through rate reductions, or one-off credits in a billing period.