Long time lurker.
Just saw an interesting notice on release of Elementary OS that has specific work done on the EUFI and boot process. Thought maybe they may be able to assist as I believe that is one of the challenges in Haiku.
"EFI & SecureBoot
With the help of incredibly useful tips, advice, and code snippets from Antoni Norman (aka Pinguy), Cody has almost completely rewritten our .iso build system since 0.3.1. We’ve tested these new builds on 64-bit (U)EFI, and BIOS machines, with and without internet, with SecureBoot and legacy boot, and everything in between. No more infamous GRUB boot error!"
Link to notice: http://blog.elementary.io/post/134884577281/freya-032-released
Just a thought. I may be way off base, but trying to assist.