Slitherine

My seleucid army is combined arms. With 2 groups fo cats, 2 groups elephants and 2 groups Lh making up the mounted part and 2 grops MF, 2 groups imitation legionares (4's) and 1 group of pike (12 bases) for the foot part with some poor LF for fill.
I does seem like I'm using too many toys, but the foot and mounted can function seperately and are very effective when coordinated well (the challenge of getting that right is a large part of why I enjoy the army so much) or the elephants bridge the gap quite well.

I was considering replacing the legionares with pikes (a group of 8 average pike is cheaper than 4 legionares) or should I leave it as is with the more manouverable legionares supporting the pike?

I'd say it doesn't matter that much but i's leave it as is. The legion is pretry much as good as the pike against foot and is better when shot at. Legions are more vulnerable to lancers but your elephants will keep those honest.