Since the latest Dec. 21 patch, it is no longer possible to adjust the TAA via the engine.ini file. Previously, what I would do is add the following lines to the end of the engine.ini file:

r.TemporalAACurrentFrameWeight 0.2
r.TemporalAASamples 4
r.Tonemapper.Sharpen 1

These settings make the TAA sharper. I do not believe this leads to any competitive advantage as options for no AA are present and no AA will always be competitively advantageous.

If you insist on blocking engine.ini modifications, please consider changing your TAA implementation to alleviate its blurriness.