Need Control over Header Indexing in HPack

Presently, it seems that the Header/HPACK process in H2 is opaque. However, sometimes it is necessary to control how headers are indexed (or re-indexed) into the HPACK dictionary.
(e.g. https://tools.ietf.org/html/rfc7541#section-6.2.1 )

Specifically, I am writing a tool which pushes via Apple APN. It has requirements for some, but not all of its headers to be set differently, based on whether it is the first send of the request, or subsequent ones.

From Apple's docs : https://developer.apple.com/library/content/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/CommunicatingwithAPNs.html

The :path value should be encoded as a literal header field without indexing

The authorization request header, if present, should be encoded as a literal header field without indexing

The appropriate encoding to employ for the apns-id, apns-expiration, and apns-collapse-id request headers differs depending on whether it is part of the initial or a subsequent POST operation, as follows:

The first time you send these headers, encode them with incremental indexing to allow the header names to be added to the dynamic table

Subsequent times you send these headers, encode them as literal header fields without indexing

Start by locating the HTTP/2 header and HPACK encoding entry points that currently make indexing opaque, then read the RFC 7541 section and the linked APNs requirements. Determine the API and scope needed to control indexing for individual headers, and verify that initial and subsequent encodings can be distinguished as requested.