I don't think anything that's been discussed about Lechmere dismisses him for being the ripper. not this psychopath argument, or the blood evidence or the timing issues. Now , obviously Fish has not proved all the three above from his view. conversely, while others have pointed to the above as having holes, nothing yet rules him out, like say Ostrog.
we still have the name discrepancy, and the fact that he is the only witness/suspect that is seen near the dead victim before rising any alarm. we also know his work route brought him near the murder scenes around TOD and the mothers house connection near Berner street.
Hes also one of the few suspects that actually has any physical ties to the case.
Sure, probably just a witness, but at this point he cant be ruled out-far from it.
__________________ "Is all that we see or seem
but a dream within a dream?"
-Edgar Allan Poe
"...the man and the peaked cap he is said to have worn
quite tallies with the descriptions I got of him."
-Frederick G. Abberline