It is a major change to ask but I am wondering if they consider to switch to asyncio instead of using Twisted. Twisted is great library but it is a huge dependency to maintain.
Some links:
* POC for aiohttp as a http handler: https://github.com/scrapy/scrapy/pull/1455
* some thought about how to make async/await API for Scrapy; it is not all roses: https://github.com/scrapy/scrapy/issues/1144#issuecomment-14...
However, as you said, it'd be a major change and it would affect the whole ecosystem (plugins and extensions), so it's complicated. We'll see what happens. :)
What I was trying to tell is if Scrapy uses only small part of library, it may be possible for developers to use similar constructs from Python's standard library. In any case dependency is dependency and it is always better to minimize code footprint.