Not the preferred way, but while waiting for an official Splash plugin in Icenium, you could use this:
GUI APK Tool for decompiling/recompiling APKs
I haven't tried it myself, but I am going to try soon to:
- Build APK with Icenium
- Decompile with this tool
- Add the plugin I need
- Recompile APK
A few extra steps, but maybe worth the effort.