2nd thought
I didn't quote you so I wrote from memory, now reread your post:
Pretty positively you couldn't separate the IR from the rest of the F1-training: The syllabus has to sort of "expectedly" last 9 months (Ari Ben fastest foreigner was I believe about 3,5 months, I did 0 - 250 hrs CPL ME/ IR in two stages in 5,5 months, but 9 months seem a realistic average at 141 academies with full ground school), plus you need the TSA clearance for the first rating (PPL in your case), ME and IR. So - I'd be surprised if the State Department fancied you applying for a 9 month training with subsequent OPT and confirmed that OPT even though you only did 10 hrs of instrument training.
You can assemble quite a list of legalese on this issue but you put yourself at the mercy of a bureaucrat who can even make an arbitrary decision on this field, based on the intent to twist some rules that generally say "show us you have 55 k $ plus living expenses, undergo 9 months of professional training and then we may allow you to work a bit in that field, for 12 months, like we would allow a foreing medicine student or attorney to assist on surgeries or intern at a law firm", not to have added competition on their quite mediocre labour market.
As for the lingual skills, there are some schools that cater specifically to foreign PPL tourists - but if those skills are that helpful those schools might even sponsor you. But would you rather teach men in their midlife crisis in the pattern or do some instrument or ME training to some fellow hopefuls? I suppose the latter will help your resume more. Again, just my 2 pence, but putting the cash aside, choosing one school carefully and sticking with them with the intent of reaching 1500 hrs after 18 months sounds like a less troublesome proposition.