I think you mean this paper:
Joanna's (Qubes OS Founder) blog  is a gold mine when it comes to hardware-software boundary security. Especially "State considered harmful"  and "x86 considered harmful"  papers are eye-openers.
For a very good explaination on that topic, see the following 32C3 presentation:
"Towards (reasonably) trustworthy x86 laptops"
Also, the paper by the author is worth a read:
"State considered harmful - A proposal for a stateless laptop"
I think you may be interested in a development of a stateless laptop  by Joanna Rutkowska. They are trying to prevent any data storage outside of the user knowledge and control.
>What could one do to make it possible to have ME-less x86 in the future?
One could lock all the devices that can store data: https://blog.invisiblethings.org/papers/2015/state_harmful.p...
"The general idea is to remove the SPI flash chip from the motherboard, and route the wiring to one of the external ports, such as either a standard SD or a USB port, or perhaps even to a custom connector. A Trusted Stick (discussed in the next chapter) would be then plugged into this port before the platform boots, and would be delivering all the required firmware requested by the processor, as well as other firmware and, optionally, all the software for the platform."