Originally Posted by SpeedbirdLHR

The international to domestic connection is indeed an issue and one that isn't as easy as it may seem. It is something that BA is very aware of and have been since day 1 but much of it isn't within BA's control.

Boarding pass check/re-print is a BA task.
Immigration is a UKBA task - they have to check everyone entering the UK. That can't be changed. They do not have access to BA systems and are not BA agents so can't check/re-print your boarding pass.
Biometric check is controlled by BAA who are mandated by UKBA/UK government to have process to ensure that only those who are allowed to be in the UK are the one who are indeed boarding domestic flights. Could this process possibly be combined with the immigration process.....possibly, but that would be for BAA and UKBA to determine and agree. Again, the agents who perform this are not BA agents.
Explosive check is again a UK government requirement and as is done for those checking in landside T5, this is done before the main security check.