Since this is the first time we are being introduced to planeswalkers, is it a good idea to have a 2 color one? What was kinda cool about the design of the originals was they had abilities that were all very basic for their colors. Is there a way Ashiok could be mono black?
Ashiok could be mono-Black without issues, I think. In fact, Ahsiok probably makes more sense as a discard-based mono-Black planeswalker than Liliana. Tightening the mechanical identity for each planeswalker isn't exactly the point of this exercise, but it's worth considering (Jace shouldn't get everything that's Blue. For example.)
It's a bit two fold really. There's no necromancy on Lorwyn, for one, so even beyond being human, her specific brand of magic doesn't fit within the setting. Aside from that, she's a LOT more of an urban person than any of the other walkers, even counting Jace. Lorwyn, being so rural, means she has an even harder time fitting in. Seriously, can you imagine her roughing it?
Fair enough. Although I guess she could be convinced to rough it if the rewards are high enough.
One thing to note here is that this makes Agents of Artifice the first time we see Liliana. I don't think that's a terrible thing, but she probably needs to show on the cards before Innistrad. She could be on Grixis, or the core sets could be used to introduce new story elements.
We could have him tracking Chandra in an early start to Purifying Fire. Leave it intentionally vague to start and then have him show up on Kephalai.
I guess that would work. Too bad there isn't something completely horrible going on Lorwyn that would distract him. (I like the idea of Gideon constantly getting distracted.)
One thing that's a bit less important but might be fun to thin about: Which moments should be the "five pivotal moments" that get their own card or each set? Or is this something we introduce a bit later? (Later might be better, because the focus isn't yet on the planeswalkers here.) I do think we should probably have
some cards featuring the planeswalkers, but those could be as simple as "Jace makes himself appear as an Elf" or something. (Maybe we should hit up YMTC for this?)