As a minor note, I think disabling SIP is sufficient, which is significantly less dangerous than disabling AMFI.
I must have done something wrong because I wasn't able to get it working without (temporarily) disabling AMFI.
My personal recommendation would be to pay for a yearly developer membership, but if that's not possible then, yes, the alternative would be to disable SIP.
I may decide to purchase a paid developer account in the future, but I do not think installing personal-made drivers for personal use on personal devices should require a choice between a yearly subscription or disabling important security mechanisms.
That's certainly something you can file a bug asking us to support, but I wanted to make it clear what you were asking for.
Where would I file such a request (/ "bug")? Even if filed, I worry that it is unlikely for this issue to be addressed in reasonable time.