I do like the idea of a modular IR. I have two issues:
1) Given that FCL.008 appears to be set to propose an ICAO-standard IR with 25 hours of training (ICAO minimum is 10), why do you want to make it difficult for PPLs by adding a further 15 hours of training to get an IR and making the (1)+(2)+(3) version sub-ICAO?
2) Since any IFR flight in an airspace system other than the UK's is likely to require flight on airways, isn't (1)+(2) as much use as a chocolate teapot -- oh sorry, I think that simile might be taken.
For a properly pan-European rating, wouldn't you do (1)+(3) first, since that's the easy bit, and get them a bit of experience in weather and the ATC system while they learn to fly approaches for another few hours?