I know I'm a bit late with the second part, but I need to get these suggestions off my brain regardless.

First Slave Backstory:

Compared to Srife for Power, the first slave we get feels kind of lackluster due to the lack of a backstory. 

In SfP your first slave had an entire backstory, deciding how you met them, and there were events that build on that and later even influenced traits the Servant would get. 

The suggestion here would be to not let the first slave be handed to you by the guild, but rather be someone you already bring with you like in Strife for Power. Even a carbon copy of the choices and events would already go a long way, considering that said servant will likely stay with you for the rest of the game. 
The guilds involvement with them should imho be kept minimal, unless they get better integrated into the story. Maybe training in their initial class or just gear for them. 

Chapter 1 Alternate End:

An idea should you ever have the time for that, as I think the civil war feels a bit short: 

Since the story suggests you getting sold into slavery yourself if you fail to make the goal you and your slaves could get bought/liberated by the rebellion, allowing you to join them instead of the guilds during the war as a second chance at the game, and you only fail if you also don't manage to beat this alternate story. 

The only guild leader that would really need replacement there is Duncan and Myr, for whom we already have a good candidates with either Aire or Gregor. or a completely new character. 
Alternatively, they could get replaced by Paperdoll characters. 

In this version of the story you have two mini  branches: 

You excel as much as Aire suggested in the current story, and actually win the war for them, giving you a noble title and being able to court Anastasia with her answer depending on similar factors as in the main story.  In this version your mansion is being referred to as "castle" instead as you'd move in with Anastasia. You'll be referred to as either King or King-Consort, depending on whether Anastasia is allowed to rule in their society 

You fail to, or don't try to court Anastasia, in which case you'd move back into the mansion, and get the title of governor over the town instead. You cannot get Anastasia (and potentially Aire) in this route. 

Zephyra: You don't meet her while taking the Settlement, but rather a bit later, when she does the Shield over Aliron instead. 

The Elven Capitol part: not necessary in this version of the chapter, alternatively Duncan and Myr flee there instead of Anastasia