I want this. Is there a third-party thing for this?
GODOT engine can compile to IOS. However, the actual BGE would have to be completely rewritten to be correctly run on the IPad; partly because IOS uses OpenGL ES rather than standard OpenGL.
Even if the BGE did start using OpenGL-ES, the prospect of it supporting iOS will never happen because of the GPL license (FOSS is all but banned on those systems).