@Level Attitude: Billie Bob and I agree.
FCL.910.FI FI Says that the FI is restricted in certain cases, and teaching for the IR is not one of them. So maybe a FI restricted may not teach for the IR, but it's not what FCL.910.FI says.
The FCL says
FCL.905.FI FI—Privileges and conditions
The privileges of an FI are to conduct flight instruction for the issue, revalidation or renewal of:
(...)
(g) an IR in the appropriate aircraft category, provided that the FI has:
(1) at least 200 hours of flight time under IFR, of which up to 50 hours may be instrument ground time in an FFS, an FTD 2/3 or FNPT II;
(2) completed as a student pilot the IRI training course and has passed an assessment of competence for the IRI certificate;
I could find no other prerequisite for the IRI course than 200 hours IFR if you are a FI or 800 hours IFR if your are not.
My conclusion is that, unless someone finds something I could not find by myself in the regulation, a FI restricted with 200 hours IFR may undertake the IRI course and teach for the IR if he/she passes the assessment of competence.