Thats what I'm thinking.
What you could do is find someone with a USBMap already made and edit it so that in includes all ports. Like, HS01-HS15 and SS01-SS10.
Then enabled the XHCIPortLimit.
If you search around there is likely a diagram of your motherboard with your ports and headers labeled.
Attached is a kext for all USB ports enabled. You'll need to turn on XHCIPortLimit though.
Note: This is for iMac 19,1. If you have a different SMBIOS you'll need to right click the kext, show package contents, and open the info.plist file with a plist editor. Then change all instances of 19,1 to your model number (ie 20,1).
If you already know what ports you use then you should open the info.plist and delete the ones you don't. If you can get it under 15 then thats great as we can disable the XHCIPortLimit then!
If you know which ports are your USB 2.0 headers then please change the connector type to 255. Currently all ports are set 3.
255 = Internal
3 = 3.0 (we use this for 2.0 and 3.0)