I think some assumptions may be wrong here: Flow doesn't need Parsoid because we integrate with VE.

As you may know, Flow is (currently) able to store content in either wikitext or html.
In production, we chose to store data in html, so that we need less resources to keep recompiling the wikitext to html when the page needs to be displayed.
Parsoid is indeed resource-intensive, but less so than the alternative of converting all wikitext to html for every request.

In this scenario (storing html), we need Parsoid to make it possible to edit things (in wikitext) that have been stored in html: plain old PHP parser can't convert html to wikitext.
Since we recently added VE integration, Flow also needs Parsoid to convert from VE back to wikitext editor.
The reason we *need* Parsoid (in production) is not VE, but wikitext-editing. Actually, we wouldn't need Parsoid if we *only* supported VE (we could just store VE's html output).

If you don't want to use Parsoid, you (currently) can, but:
* you have to store content in wikitext & convert to html for every request (will need lots more CPU, depending on amount of requests)
* you can't use VE (since we can't convert the html back to wikitext)

We currently still support wikitext storage/non-Parsoid (in part because we simply have to: jenkins isn't set up to let us connect to Parsoid yet) although it's suboptimal (see above).
We must face that it's a burden to maintain & we just can't test everything all the time. Things may be broken from time to time.

We don't need Parsoid because we have resources to burn, or because we want to push VE; those 2 would be easier without Parsoid & compromising on other things.
We choose to use Parsoid because it is the best (only) solution to be more conservative on resources (store in html) & still support editing one's post in wikitext.

AFAIK, there are no concrete plans to abandon wikitext storage/non-Parsoid support yet.
I think we can put this discussion to rest at least until we can contact Parsoid on jenkins, which may or may not be awhile.
I'm also going to close {T88908}