Hi Snake-Eyes,
The G-Core, at least the MHS versions, are designed to attach to the copper BH heatsinks, so yes, you could just as easily swap out another led/heatsink setup with a mini QD.
The channel behind the charge port isn't for sound per se --it's more to allow air into the core itself so the speaker has something to move behind it. In reality, the speaker on the prototype core pictured faced forward, and is near the base of the crystal chamber. The square grooves are the main speaker "holes", and the crystal chamber itself is vented and designed to act somewhat like a resonator. 'Still working on the design as I said, but for not it is satisfyingly loud.
Also, the extension is good idea, and one that I've been tinkering with some time now. The problem frankly isn't necessarily length, because as you said, that's easily circumvented by providing an extension piece (mathmatically there aren't *too* many of these to solve for 90% of MHS saber configurations). The real problem is the varying IDs when you introduce other parts. The male/male adapters, for example. Or the chokes. Or most obviously, the ribbed sections, which are narrower than the main body sections. As stated earlier, a single chassis cannot account for that many configurations. "Modular" is both a requisite and a limitation.
For now, my plan is to make a couple versions as earlier detailed, that will be compatible with a good number of MHS configurations. 'Enough to make people most people happy. As they say in business, it isn't about making every single product that will sell --it's about making the products that will sell well.