As far as I am aware the ATPL is only really applicable to multi-crew operations. I am not quite sure why the old CAA ATPL was issued without the requirement for multicrew time but maybe it did serve some other purpose? (insurance maybe? any comments?) Still why would you need an ATPL for single pilot operations?
Under JAR there are two situations where an ATPL for the commander is required. Off the top of my head i think they are: IFR for helicopters with more than 9 approved seats and VFR for helicopters with more than 19 seats (JAR-OPS 3). Pilots going into those sort of jobs will not have a problem with gaining the required experience.
One problem does however arise for operators of large mutipilot helicopters (>19 seats) operating VFR only. In order to obtain an ATPL those commanders will still have to do an instrument rating even though they will never fly IFR.
This I believe is currently addressed by the JAA and there are moves underway to introduce a JAR ATPL(H)/VFR (as described by ICAO). Still multicrew but no requirement for IR.