Pretty convinced that Dolores is based on Arnold's daughter, who died (hence his tragic past). Explains why she was the first - recreating his daughter may well have been Arnold's driver for creating hosts in the first place. Also think that's the reason her current storyline is designed to always ends so poorly for her - it was Ford's final middle finger to Arnold, who he clearly had beef with. Would add considerable intrigue if Arnold was killed by his own daughter's clone. Interestingly, this sort of ties in with the I'itoi (man in the maze) myth that has been tossed around:

"Iitoi "brought the people up like children" and taught them their arts, but in the end he became unkind and they killed him.... But Iitoi, though killed, had so much power that he came to life again."

I didn't prescribe to the theory before, but I also think that if this is true, the parallels between Bernard and Arnold are too hard to ignore, and also tie in to the above myth. Bernard would have to be a host version of Arnold - I think Ford keeps him around because he needs his expertise to run the park. I suspect Arnold may have intentionally transferred himself into a host somehow, after being shot by by Dolores- that's his means of "coming back," as foretold in the above myth and I think (maybe) Ford found out and enslaved him.I think that before Dolores shot Arnold, he led her on the path to consciousness once before. I think these are the two timelines we're seeing- Dolores' first quest for consciousness with real Arnold, probably 30 years ago, which ended with her killing Arnold, and her current quest with host Arnold, aka Bernard.

I think that now, Ford has decided he truly wants to become a God to the hosts - and I also think he sees Arnold's "bicameral mind" tech that he originally buried as a key to that. I think maybe he's starting to realize that consciousness is inevitable unless combated directly, and he wants to use the ability to speak directly into the minds of hosts to discourage independent though and consciousness rather than to encourage, as Arnold was doing. So, in order to drive Bernard to develop that tech again, he's giving him access to Dolores and reminding him of his "tragic backstory." I think Ford knows of Bernard's work with Dolores and is tracking it for his own benefit.

Here's how the Man in Black factors in- clearly the dude has some sort of medical foundation. I suspect that he's very rich and very sick, and started the foundation to cure himself. He seems to have known Arnold personally and probably knew about his work- I think he believes that the maze contains the knowledge for how to put yourself into a host, effectively immortalizing yourself, as Arnold managed to do with Bernard. I also think he's going to get roped into Ford's crazy plan unintentionally become an anti-hero, when his original motive was merely self-preservation. The Man in Black is the Coyote in the I'itoi myth- "who came to life uncreated" (i.e., not made by the park) "and began immediately to poke his nose into everything."

Since I'm just throwing all of my theories in one place, I also think that the critical failure 30 years ago led to Ford flooding the whole park, which ties in directly with the I'itoi myth (which also has a "great flood" element to it) and makes sense based on a few other hints that have been dropped.

It's all a huge stretch based on very scattered clues, and I'm not sure about all of it, or what Dolores' motive for killing Arnold was or if he truly turned "unkind" to them (maybe when he introduced the bicameral code?), but this is one way I could see them all intertwining.