'…
why did Boeing go through with MCAS and not just simply declaring the behaviour and asking for relief? '
This is likely to be the financial 'dazzle' of commonality with previous versions.
The MAX might have met the requirements, but it may not have been sufficiently similar to a 737' for the minimum-change training objective (valued at $1M / SW aircraft).
'
Angle Grinder devices, or strakes'
An example;
https://www.rafmuseum.org.uk/researc...-demonstrator/
The the leading edge extensions and mass location deliberately destabilised the aircraft.
The experimental control system provided the basis of a quadruplex 'FBW' poof of design and certification (*) for future military aircraft - Typhoon, and for the B777 flight controls, but with a Boeing (stick-force) algorithm.
The 737 Max may not have warranted this level of design, but did require equivalent certification. The dominating bias was commerce - simple low cost, quick, time = money, and 'the same as previous 737s'.
Conversely, all to often we seek to use the latest technology; e.g. use Artificial Intelligence, but not always understanding the need for it.
Instead of AI we need 'IA', Intelligent Assistance.
With hindsight, MCAS was designed to assist, but it wasn't intelligent.
* for the technophobes -
https://apps.dtic.mil/dtic/tr/fulltext/u2/p002713.pdf
fdr, yes please - see pm.
Clean wing - you overlook the 146/RJ. Not a VG in sight; a stall breaker to ensure that the inboard wing stalled before the tip. Same aero team as the early Airbus wings.