The real issue is that OGC has not yet adopted an approach for vector tiling. What is the content encoding for a vector tile? Is it Protocol Buffers (as per Mapbox Vector Tiles - MVT)? GeoJSON? Something else? OGC members are reluctant to support a vector tiling approach that is only used with GeoPackage. (Supporting one-off solutions often has a poor cost-benefit story.) OGC simply needs to make a decision and a community standard would suffice.
Once OGC makes a decision, it is a straightforward matter to support it in GeoPackage. We would create a new extension that would define a new content type that depends on the tiles option. I don't think there would be any other ancillary tables like were needed for tiled gridded coverages, but if there are we can add those. This would get us to a community extension which will satisfy some people. If we want an official (OGC adopted) extension then we have to go through the normal process of OAB approval, open comment period, TC vote, etc. This process will probably go smoothly as long as we have proof of implementation.
UPDATE: After talking with a few people, I went ahead and drafted a community extension based on the MVT approach.
UPDATE #2: In response to this issue, OGC initiated the Vector Tiles Pilot.