What does MFS-3 mean from both Kiryu films?

MFS-3 Type 3-Kiryu is the official designation for Kiryu by the J.S.D.F. I'm not sure if it actually stands for anything, but it is Kiryu's codename.

Multi-puropse Fighting System 3 Type 3 Kiryu

I wonder what Multi-puropse Fighting System Type 2 and 1 where suposed to be, Withe Heorns and Massers?

Where did you get it?

The Maser tanks in the Kiryu Saga are Type 99, so I'm not sure if type number matters.

In Japan the "Type" designation is used to label military equipment accepted during the new fiscal year. (Japan's fiscal year starts in April.)

Kiryu was completed in the year 2003, four years after the new Godzilla's first attack in 1999. Thus Kiryu is designated "Type 3" for the year 2003.

The Maser Tanks seen in Godzilla x MechaGodzilla are Type 99 for being accepted as the top of the line model in the year 1999.

Cool.

Multi-purpose Fighting System-3.

You're welcome.