Well, remember, Masters can fight Servants and win, but they must be fighting using their strongest point and against the Servant's weak/mediocre points, hence the stated gap(A 3 PL gap between the baseline means the Master can make a stand via power stunts or their speciality, provided the Servant isn't using their Noble Phantasm, they can even pull off a close call win if they used their most powerful ability, with severe drawbacks and power stunting to fight a Servant that's arrogant enough not to use their strongest weapon).
Highlights are(Spoilers, if anyone looking into this game doesn't know already):[spoiler]
-Rider vs Kuzuki, it's offscreen, but presumably she got surprised the same way Saber did. It's unlikely to be Caster given the close quarters and the lack of smoking craters.
-Kuzuki vs Saber(using his martial art against her, with Caster bolstering his damage and stun DC, Saber is not using Prana Boost nor Excalibur yet)
-Rin vs Caster(using her limited use(10 gems) magic to counter Caster's baseline magic and punch through her toughness, Caster's Noble Phantasms not used, not in her workshop with the precasted artillery arrays)
-Shirou vs Gilgamesh(using his strongest ability, Unlimited Blade Works and power stunting like mad, to constantly counter Gilgamesh's own 'baseline' ability of Gates of Babylon, Ea, as his strongest Noble Phantasm was not used, nor was Gilgamesh's armor.)
-Shirou vs Archer didn't really count, considering Archer was likely throwing the fight. It was a battle of ideals, not skills
-Matou Zouken vs Archer, Zouken is 'killed' but he manages to survive using his unique skill of being a Worm that Walks. This allowed him to also survive being smashed by Kotomine and then by Sakura. Being a 'soft' defensive ability, it's hard to gauge it's effectiveness.
-Kotomine vs True Assassin, Kotomine holds his own in a fight using one of True Assassin's weak points(Hassan's not a great fighter for a Servant) and uses his special ability(heartless? hes certainly hard to kill) to counter True Assassin's Noble Phantasm. His Keys manages to pin True Assassin, but are themselves limited ammo.
-Shirou vs Berserker, Shirou uses Archer's arm to fully project Nine Lives Blade Works, to defeat Berserker's Noble Phantasm of God Hand. Archer's Arm is his special ability in this scenario, with an extra nasty flaw in that it kills him with overuse. It's probably mental stat drain.
-Sakura vs Gilgamesh, Sakura as Embodiment of the Black Grail uses the shadow to eat Gilgamesh and use his energy to regenerate her wounds from Gates of Babylon. Gilgamesh's fatal flaw is that he was going to let her bleed to death, instead of killing her thoroughly. As the Embodiment of the Black Grail, this has a bunch of drawbacks, but mostly, that it makes her evil and very hungry.
-Shirou vs Dark Saber, Sparks Liner High is one of the premier cases. Shirou uses Archer's arm to a fatal extent to beat Saber, but up until he ran out of things to drain, he was dealing with it blow for blow.
-Rin vs Dark Sakura, technically not a Master vs Servant fight, but it's arguable that Rin replaced her 10 gems(which weren't used) with the Sword of Zeltretch and started hurling Servant class beamspam around. Being a projection, the Sword probably wouldn't have lasted very long, so it as only good for a single fight.
[/spoiler]
In either case, it is your game, don't feel particularly compelled to follow the above. Masters beating Servants happen, not often, but they happen.
Still, how do you plan to work the game?
One player running a Master/Servant pair?
A player running a Master or a Servant, linked to another player with a matching unit?
Are players allied(2 Master/Servant pairs teaming up) or is it a free for all(every man for himself)? The former is better for small groups, the latter needs secrecy, or at least a gentleman's agreement not to peek in the other team's activity.
