Indeed 4 points...
1) 6-layer boards
On my WishList I have 6-layer boards.
2)
Another point is 35\my\ of coippeer on inner layers
3)
The option to have vias or holes in SMD pads metal-filled (as some PCB manufacturers offer). Or the simplified "poor-mans method" to add a third solder-mask which just adds "lids" over the holes on top or bottom side; controlled with an additional "Via Key" layer.A "SMD pad with a hole" is a pad defined as a through-hole with the top-layer shape the shape of "the same" SMD pad, a circular shape in other layers.
4)
How difficult would it be to make traces, annulars etc. 0.1500mm, today's lower limit 0.1524mm (6 mils)?

Generally speaking, I see you with your pricing as the "final resource" for the Hobbyist. Definitely realistic for the Hobbyist to make a good PCB instead of "messing with" primitive lab boards, etc.

/dindea (Staffan Cronstrom)