Another good point is that all the choices carried over are pretty much entirely superficial and there really hasn't been any cross game branching so far.
Pretty much. It doesn't surprise or disappoint me, because it is what I have to come to expect from Bioware. They have done this in so many other sequels before, where they can't spend the resources (understandably at times) on establishing continuity, so they create plot devices to cover these shortcomings.
The real reason why Ashley wasn't in the second game beyond the cameo was because she had been a romance option in the first game, and it would taken a lot more writing and voice acting to account for the various possibilities.
Basically they would have had had to have written dialog for the following Ashley scenarios:
People who had romanced her in the first game, and wanted to continue in the second.
People who hadn't romanced her in the first game, but wanted to now.
People who hadn't romanced her, and didn't want to now either.
People who had romanced her, but wanted to break up with her, yet still remain friends now.
And then there are other possibilities, like people who romanced with her but then broke it off with her for Liara etc.
Even the meeting with Liara in ME2 was carefully positioned so that it would happen before any romance could begin in the second game.