1. They are responsible for the magicks used to create the original slayer. If it would be possible to apply any rules to how the line continued, they are the only face we can put to who would be the ones applying them, at the time of the original spell.
Yes they begin the process, no issuewith that, but there is no real evidence that they have control after that first girl.
2. They are responsibe for the force within the slayer referred to as her "truest strength". Translation. It's current. What they did 10,000 years ago is still happening, still with the slayer.
Thats fine, but why is that? Because they intended that to happen of because something higher helped it along the way.
We are also led to believe that the Shadowmen turned into the Watchers, yet there is no evidence they wield any power of the girls at all, only guide who they find. We don't even know how they know which girl is a potential.
3. They have shown an interest in the line of the slayer at the beginning, and also at the end.
Again, like i say, the First Evil has shown interest in the line along the way....that only proves they have decided to 'watch' something they set in motion....not necessarily control.
4. Their cave is "the source of slayer strength".
"The well of the slayer's power".
Thinking about what PJ just wrote, we aren't even sure of that. We see the Cave as a representation, but now that its thought about, that cave might never have existed, it could be some artificial contruct the PTB's have designed to allow the Slayer Strength to live on after death.
5. The writers chose to present the possibillity to us the Shadowmen were connected to the slayer, her creation, and her continuing story.
Well yes, they also chose to tell us that every event in Angels life had something to do with being that needed to be born through Cordy, kill alot of people then wash that murderous spree away as a hormonal imbalance!!!
I see what you are saying here, i do but the writers have changed many notions we have come to accept as easily as...Vampires can't have Children, lets get Darla pregnant.
The Powers That Be of Angel are responsible for how Slayers are chosen
1. I'm not sure I can think of any support, other than some viewers kind of like the idea.
2. The Powers that Be are Present in the Angel verse so must be in the Buffyverse in some form. We also know the PTB's have a vested interest in the fight against evil.
3. The Show never Specifically states that The Shadowmans actions choose which potential is worthy, its random in nature, yet the Powers use in Angel suggests nothing is random, its all destiny and fate.
4. Whistler is regarded as some formof emissary for the PTB's(debateable granted) but he apparently knew of Buffy's calling at the same time if not slightly before the Council, suggesting something told him....if there is the link with the PTB's they could tell him who the next chosen is......(i know, all supposition but some of your points are
😉 )
Like i say, i'm not gonna change anyones mind who already has an opinion, all i'm saying is, your points could be argued away better and mine argued better(if it wasnt 2.45am) by someone.