"Ah yes, Sith Sword Combat... the sword combat equivalent of throwing a tantrum to get your way"
The Sith have always emphasised strength, no matter the timeline or period. It is fitting that a weapon purely built from the Dark Side requires a great physical strength to even wield it, showing the Dark Side has never generated strength, only corrupting that what was already there.
Sith Sword Combat emphasises heavily on one’s connection to the Dark Side according to the author, and reading through his texts, I know from my own relationship with the Dark that it is likely one that requires constant emotion poured into the blade. A foolish endeavour to anyone but a Sith. Regardless, one can alter the weapon’s molecular structure itself, using the Dark Side to make it stronger and sharper, or even being able to absorb blasters and other energy based projectiles. All of the while, the blade makes the user stronger in the Dark, until they are consumed… becoming a Nexus itself.
[Mace often talked about Force Nexuses with a degree of caution and yet reminiscence; and with all the battles he has fought, I oft wonder which one he used to think about - Un'duro]
As such, I would guess the best approach would be to extend the fight as much as possible, allowing a power build up to occur throughout the fight. Thus, taking an approach like Soresu may be useful, though such an approach would likely become more difficult as one thrusts themselves into the Dark with each second. The mind, like the sword, gathers energy until it explodes with aggression; the uncontained hatred of the Dark Side spilling forth into a furious flurry of attacks. Something to be utilised by an opponent…
Its relationship with lightning is particularly interesting, which can be absorbed into the sword and then released in one large energy burst upon contact with a substantial physical object. As such, it would be in one’s interests to generate such an effect throughout the fight when using lightning regardless. Changing the strength and sharpness throughout the fight would be of interest as well, throwing rhythmic opponents off guard, though such subtlety may become difficult as the Nexus grows.