Can you get a Passive ASIC?
Not an expert answer, but some disconnected relevant facts:

One of the reasons that ICs often require external passives is that standard silicon ICs are not a good substrate for making capacitors and inductors of significant value on-chip. Thus, a conventional IC, "AS" or not, is not a space-efficient way to put large passives on a board (other than high-value resistors). It might still work out to be an improvement if it's not the value but the number of parts that is a problem (i.e. packages and interconnects account for most of the area), but this is why, for example, your microcontroller always has external decoupling capacitors.

Resistor networks and capacitor networks are an existing common form of passives-in-a-single-package. I haven't heard of any mixed passive types in a single package, though — I expect it would be difficult in the same way as putting passives in a normal silicon IC because they have very different materials and manufacturing techniques.

Resistor networks can be used:


To save space on the board; they were much more common and relevant in the through-hole days, I believe, where even if you placed the resistors vertically you would need an entire hole for the other pin, and a network would let you have \$N\$ resistors with only \$N+1\$ pins).
As a high-precision voltage divider or other configuration of matched resistors (this is often seen in high-end measuring instruments). Multiple resistors made using the same process and on the same substrate can have tighter tolerance, more temperature-stable ratios of resistances than independently manufactured resistors.


Hybrid integrated circuits, or hybrid modules, are sort of an intermediate technology between PCBs and single-semiconductor-die ICs, which can include passives either formed on the board itself or soldered on — but they are not noteworthily compact nor cheap. The value is in having a precise, pre-built, sealed module that you can plug/solder into a larger board.