The improvement compared to current Lich?
Once again, it's right there in the cores.
Lets look.
Current live is this:
Lich gets +2 Int Base. +2 Int from Tier 5 ability.
And also +2 Int from Capstone.
They also get an innate +1 to Necro DCs.
That's +6 Int and +1 Necro DCs.
Proposed Changes:
Lich gets +2 Int Base. And that's it. But theyve moved that missing int from Lich, INTO the Capstone
Which now gives +4 Int
And you can now choose to get +2 to Necro DCs out of your cores.
That's still +6 Int, and +2 Necro DCs.
That means you are doing 1 better than normal, BUT it ALSO means that since the power has been moved out of Lich specifically, and into general options and the capstone, you can get that +4 Int and +2 Necro DCs on any form

So you can be the Wraith you apparently always wanted to be, WITH your 35% incorporality (As I covered above) and still be on par with Lich, since Wraith gives +2 Int now as well!
Or if you LIKE the defenses and Con that they gave the Lich, you can take that instead and still be better than you are now!