For bichord/trichord one way to do this would be to have monochord arpeggios and use 2 or 3 parts where all 3 PARTs are the same including the arpeggio. Depending if you have the 1st part only or 1st+2nd or 1st+2nd+3rd will determine if you have monochord, bichord, or trichord. You could use note range to limit only certain note ranges to bichord vs. trichord.

This might not be very efficient (in terms of Part usage) - but it's easy to accomplish.

I don't know of anything that is melody intelligent. There's chord intelligent where the arpeggio looks at the trigger notes used and infers, with rules, the chord. I do not consider this to be any component of melody.

Octave jumps I'm not sure exactly what you mean. Jumping an octave away from your trigger notes or following your trigger notes if they move to different octaves.

Not sure how many simultaneous notes you want trichord - this could eat up polyphony fast.

In a perfect word, where samples are easy to come by and easy to create fully polished instruments - I'd probably prefer to find bichord/trichord samples and use those rather than trigger multiples of the same note. That would conserve polyphony - but is hard to do if you can't just get something "off the shelf". Sampled pianos already have mono/bi/tri chord samples reflecting the property of each string of the sampled piano (because there are Waveforms with all 88 strings sampled). That's one example. But if the factory set doesn't have what you need - then arriving there through samples may be cumbersome. Achievable - but YMMV.