I did my IR / ME IR at Rainbow Air in Long Beach, and its where I'm going to take my CPL. You're right when you say the IFP test only gives you PPL IR privilages based on your foreign licence. The way I have been doing the FAA tests / exams is to:
Do the IR, so now you have the full FAA IR
Do the PPL ME and on same check ride get IR privileges by shooting two approaches, one with engine out
Take the CPL in a complex single...reason for this is that if you take it in a multi, then you have to have completed all the requirements (300nm X/C VFR day and night) in the ME increasing cost (unless you already have these requirements)
Take the CPL ME (with IR). As you already have the PPL ME then this is an 'easier' check flight, similar to the one already carried out for the PPL
Now you have the CPL SE/ME IR you can legally act as co-pilot in anything and Captain in a twin A/C less than 12000 lbs. You need a high performance endorsement for an A/C giving over 200HP per engine, though this is a simple instructor sign off though.
If you want to build hours as an instructor, you need to get a CFI rating, and once you have this I'd recommend getting the CFII (Instrument instructor) ratings.
If you have 1500hrs TT and all the requirements in the FARs then you can go and take the FAA ATP flight test.
Hope this helps a bit....
EA