As for the comment on there being better A4 launchers out there, there are not many A4 launchers geared towards supporting and keeping up with mechanized and motorized infantry in terms of speed. Most launchers as faster than the units they would be supporting, good I guess but when you are playing with a infantry heavy force, speed tends to fall by the wayside quickly so having a JES III A4 variant, nice slow and plodding like the units they are supporting does not sound that bad.
Then again, I have gotten used to the idea of speed 3/5 as not being that detrimental when played intelligently.