Whilst my comments above may just be 'wishful thinking' Richard I have long thought it would be better to 'just' remove the P38 security altogether and install my own immobilisation systems; Just a few concealed switches would do that too, plus maybe a flashing LED/steering wheel boot ! That has to be better than the woes of random lockouts and the receiver nonsense etc many of us have endured over the years.... and as a result we have had to rely on Colin/Blackbox, Storey/EAS, Marty/Rcvr etc and your own expertise (and that of others) of course on here..... not to mention RAVE !
In the meantime....
My own Rcvr. 'workaround' years ago was to use a second fob with an 'RF Relay' to turn the Rcvr. power on/off to the R ! Lost count of the number of batteries that cost me.. Truly appalling design as we all know
- Similarly the stupidity in that design was of course a wholly ineffective (first) 'upgrade' that did not work, plus the fact that the 'product' was unsuitable for purpose and yet we -the consumers- have to pay for this.
The other weakness - EKA entry via the (maybe iffy) door lock microswitches - might be mitigated against by fitting some push buttons in parallel to those micros (but easily accessible inside the car), but I did not get around to that (even though I have a pre-V36 BeCM...). Not happy having to re-design the electronics because LR lacked 'vision' !
FWIW Immobilisers have been mandatory since Oct. 98, but really something of a joke now since Keyless Ignition as you say is so easy to defeat/bypass with a relatively-cheap box of tricks ? More 'stupidity' is involved if folks have their RR stolen and then they buy an equally insecure RR with the insurance pay-off... and use a steering lock..... a common issue round here !
Also FWIW I have been asked multiple times now 'what it is like to have a classic (!) RR' .... and my reply is "you need a bucket of suoer-glue, a degree in electronics and the patience of a saint" aka 'stupidity of design' I repeat !