I don't have a clue about that side of things.
I could never justify the cost of getting the no instrument applied restriction when I was a full time instructor. So would now need to get an IRI unless I went through regaining my FI and upgrading.
And now I have loads of hours flying IFR but in a twin turbo prop and my FI lapsed recently.
So to become a FI capable of teaching on twins and single I would need.
FI revalidated which is a two day course and skills test £1000
MEP rating back which apparently is a full course now to learn how to use cowl flaps and mixture levers. £4000
30 hours PIC in a MEP £7500 (the 3000 IFR hours as PIC of a twin TP don't count)
MEP added to FI £3000
IR added to FI £1500
So as you can see from those costs there isn't going to be many Commercial pilots going to go near becoming able to teach IR. And the current PPL instructors don't have anywhere near the IFR experience levels to be able to teach it.
So in some ways it really doesn't matter what the rules are about gaining a flavour of IR there is going to be no bugger to teach it. And the few that do will be able to charge a fortune so will price most out of the market.