Adding presets would bump up the price a TON.
That would mean that every single control of the synth would need to have a digital-analog interface to the preset storage chips.
That's one of the reasons the sub phatty is twice the price. What it might lack in features it has in Mg stability and warmth (to use the common buzz word), and the whole extra digital-analog layer of circuitry, which allows for the preset storage, the MIDI CC control, the software VST settings interface.
TBH, I wouldn't want the preset storage. I dunno, the idea of it is just a little off-putting to me. I like the simplicity, the feeling that what's in front of you is always exactly what the synth is doing. It forces you to really become familiar with all the controls, to be able to patch up a given sound easily enough to make up for the lack of instant preset recall.
To get back to the original question, I think that trying to make a poly brute would be trying to make something out of the brute which is simply isn't. The architecture, the sound of it, whatever, I don't think would directly translate well to a poly synth.
Arturia making an analog poly with the experience they have from the brute? Sure! But I don't think it should necessarily try to be categorized under the same name as the original brute.