I'll just cover a few points that I thought you're incorrect about.
JMZ's saber chi is also invisible. In fact, when he dueled with the 6 monks, he lit incense sticks so that the path of the various chi streams would be visible.
Doubts aside, we already have JMZ's saber chi.It is the only sword qi technique known in JY world. (I personally have doubt about DGKB's sword qi claims).
I have to concede this because JY said the same (even though that's not physically true).Moreover, this sword techniques are launched via the finger. This enables the practitioner to adapt and launch attacks swifter than someone who can yield a sword or saber, while covering the same attack distance.
Nothing unusual in DGSD really for the high level fighters.In addition, It has a concentrated sword qi that can cut a saber.
HL28P just pulverizes rock but sure. JMZ's saber chi again can do the exact same thing though.It is long ranged- 10 feet. This is obviously shorter that the palm winds of HL18Palm or Canhe finger but none of these can have a concentrated energy to cut a metal i.e. saber.
Still kind of a waste.I would argue that the greatest strength of 6MSJ is that the various techniques of 6MSJ enables a well versed practitioner to execute multiple sword techniques that have complimentary strokes- potentially one can execute several strokes at the opponent at the same time --> thus making them unable to defend at all.
With just two swords, Jade Maiden + L/R can already execute complimentary strokes that leave no opening. A fighter with the internal energy required to execute 6MSJ could infuse two branches with internal energy and achieve a similar effect.
Since it's clear that 6MSJ is diffused by opposing internal energy, such a branch colliding with 6MSJ would diffuse the sword chi. The branch however will still continue to sail towards to accupoints even if its devoid of internal energy for a moment.
Which brings up the last problem. Now 6MSJ can execute 10 blades at once. However, if these blades are opposed by internal force, they dissipate just like any other internal energy attack. Against 10 blades, a HL18P practitioner only has to send a single double-palmed blast wave at the 6MSJ user. Assuming their internal energies are equal, all 10 blades would have to be sent out to cancel it out. If the HL18P was using something like the triple-melded attack of XF, even 10 blades wouldn't be enough.