Artillery prime mover is a class I hardly ever use
I think about the
only one worth bothering with is the one big halftrack that humps a German 88mm since moving towed 88s is useful for early war Germany until 75mm ATG are common and T/D become better heavy AT asset propositions than a soft 88 gun.
Other than that any gun or mortar I use fits in a halftrack and those are usually way faster so more tactically useful.
(Dont think I have ever used a horse limber other than one granted to me in a scenario!
)