I'm not sure on semi aggressivenesa most schooling fish aren't aggressive. What about balas sds or tin foil barbs? Although balas and barbs will either need to be replaced when too big or upgraded
Aye Thorichthys species, possibly. But may end up chasing the Texas all over if a pair forms and stuff.
I reckon Electric Yellow Cichlids would be a good choice. They don't grow as big as the Texas, but do group together usually and thus will protect each other when/if the Texas goes for them.
Giant Danios will work but do get big, other large barbs will work but not really semi aggressive. I would say a school of 12+ Buenos Aires tetra will work well in your tank, these can be feisty and have a fairly large disc shape.