for my event in north wales in April (the woodland welsh championships) I plan to add a few at the organizers discreation rules to the standard FRA rules. One of these is, no Lithium polymer batteries at all, but other lithium technology may be allowed with prior approval.
Id suggest the FRA look at the second part of this, as things like lithium phosphate saphion cells are as safe as nimh apparently.
I dont think its a lost case, you just need to make the technology info available to the FRA and event organizer.