Liberation Miniatures metal figures firing a tripod mounted grenade launcher from the collection of COL Jim. The man in the back is a Caesar Miniatures figure for size comparison.
I would use the Liberation Miniatures to fill in the gaps left by the Caesar figures. Heavy weapons like this one would not necessarily be next to the massed infantry so the difference would not be so noticeable. Also painting and basing them in a similar manner would help a lot too.
As you can see from the close of view of this ATGM the Liberation Miniatures are pretty good figures and the weapons are quite nice.
Tripod mounted machine gun and infantry from Liberation Miniatures. COL Jim mounted his metal figures on sheet plastic bases and gave them a primer base coat. The tripods are one part with the space between the legs filled in with the terrain. Looks even better when actually painted up and is very durable. These are very good as wargame soldiers.