[InputAccessoryView] Can't specify keyboard-conditional bottom padding

Environment

React Native Environment Info:
  System:
    OS: macOS High Sierra 10.13.5
    CPU: x64 Intel(R) Core(TM) i7-4770HQ CPU @ 2.20GHz
    Memory: 25.07 MB / 16.00 GB
    Shell: 3.2.57 - /bin/bash
  Binaries:
    Node: 9.3.0 - ~/.nvm/versions/node/v9.3.0/bin/node
    Yarn: 1.6.0 - /usr/local/bin/yarn
    npm: 6.1.0 - ~/.nvm/versions/node/v9.3.0/bin/npm
    Watchman: 4.9.0 - /usr/local/bin/watchman
  SDKs:
    iOS SDK:
      Platforms: iOS 11.4, macOS 10.13, tvOS 11.4, watchOS 4.3
    Android SDK:
      Build Tools: 23.0.1, 25.0.0, 25.0.1, 25.0.2, 25.0.3, 26.0.1, 26.0.2, 26.0.3, 27.0.3
      API Levels: 23, 25, 26
  IDEs:
    Android Studio: 3.1 AI-173.4819257
    Xcode: 9.4.1/9F2000 - /usr/bin/xcodebuild
  npmPackages:
    react: 16.4.1 => 16.4.1
    react-native: ^0.56.0 => 0.56.0

Description

If you have a bottom tab bar, you want the InputAccessoryView to appear above it when the keyboard is collapsed. However, when the keyboard is expanded, you want the InputAccessoryView to appear directly above the keyboard.

This sort of "conditional" bottom padding is currently impossible with InputAccessoryView. It seems that when the keyboard is expanded, the distance between the bottom of the screen and the InputAccessoryView is fixed. Attempting to change this distance with height, padding, or margin style properties does not seem possible.

Reproducible Demo

I've created a minimal repro here.

Start with the linked TabsWithInputAccessoryView minimal reproduction and observe InputAccessoryView positioning with the keyboard collapsed and expanded. Trace the React Native InputAccessoryView implementation from the reproduction to determine where bottom spacing is fixed; done means the accessory can sit above the tab bar when collapsed and directly above the keyboard when expanded.