and there is an official explanation:
http://mwomercs.com/...ns-get-removed/
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HOWEVER: Old love never dies...and with the raising number of more and more Mechs - isn't there any reason to bring it back?
Well - it isn't even a good Mech: the YLW is faster and has zombi mode
the 9A has more missiles and zombi mode
But it is still the first Mech I bought and played in MWO... it was the first Mech i scored a kill with (was a Atlas)
If you don't want to have 2 Centurions with AC 20 - I'm sure there is a way to give the AH more speed and upgrade the YLW to the YLW2 (as suggested in all those dozens of topics before)