I thought the Subaru Impreza RM is actually already a rally modification instead of a racing one, it shares much more in common with an Impreza rally version (that rear wing, those rally style wheel, think it even has 'handle bars' for the navigator) than an Impreza touring car.
In fact I only use it as a rally car as I thought that's what it's for, love to have more though (Delta Integrale and the Lancer Evo T.M. are obvious candidates).
It is a rally mod which can go better on the Road tracks than the old WRX but you don't even need it realy. just like You don't need a touring car or Japan GT mod Because they included "The Impreza Touring car" And " super GT " and a "Newer Impreza Rally "version any way. They just did not build a Premium model for the touring car which is the only advantage the current RM has .
Touring car
Aero 35:60 ( not limited buy rally specs )
weight 1030kg
BHP 527
Its a race car so in this case has a blockade placed on Dirt or snow tyres
Super GT
Aero 35:60
weight 1100KG
BHP 358 ( limited buy race rules that it entered in )
RM subaru
Aero 15:35 ( That sucks but thats the rally limitations )
weight 1065Kg
BHP 524.
Allthough we can only speculate over if All RM/race car would have been premium over time. if they had not been forced to release early, But DTM and Japan GT would have been.
The number of Race Cars in the dealership which could have been there as RM mods to the Road car seams to show RM was being Dumped for Fixed Versions.
This is what I hope they will still do. Every RM/Race car out of the UCD and in to the Premium dealership.
Its not that there are not Race mods/Race cars of road cars its that unless the User goes looking for them on GT5 car data base sites you just wont know that theres a RX7 and RX8 Race moded car waiting in car the UCD..
And yes the NSX LMP race car is waiting in the UCD as well its not a premium model race car.