Though the "en-route" bit is the easiest. We came back from Valenica a while back and the actual routing was dct barcelona dct <somevoronthefrenchborder> dct some other french VOR dct Gurnsey dct SAM then some STAR into Stanstead which became vectors. A couple of flights should suffice.
I think that training should cover all areas of operations at least once- in the case of a full IR, anything that may be thrown at you, from LDA, SDF, Back Course, ILS, NDB, GPS approaches, as well as holds, SIDs and STARs.
However in reality in JAR land, trypical instrument rating profiles go between about 3/4 airports - if you fly from Bournemouth for example, you'll do approaches at Exeter, yeovil, Southampton and maybe Alderney - over and over again until you are good enough to satisfy the examiner you can fly to these airports. Also if you book the examiner on a Friday, he likes Southampton as it is close and he can knock off early (for example).
So if the "cut down IR" only included ILS then the training can be significantly cut down, the theory can be significantly cut down, and the cost can be significantly cut down. If one is then only allowed to file to an airport with Precision approach there is no worries with ATC telling you to shoot the NDB approach and you saying "uuurrrr, sorry". It also prevents one having to buy a Crystal Ball to determine the exact weather at 10:37 at the destination. Seems very sensible to me, and the practical test standards can be equal for the enroute and approach portions.
The addition of an Oral exam, which could test the applicants knowledge on all aspects of the cut-down IR would weed out those who don't really know what they are talking about.