A discounted "through" bus fare would be excellent but could be open to
abuse - if it were based on a reasonable time allowance (say, 45 mins
between touching in on the first bus and the second) then you could make
a short bus journey, get off and do something, and get back on the
return bus.

Some while back there was some discussion about capping on the Yahoo!
Tramlink group. At the moment the requirement (*) for passengers to
touch-in before every leg of a tram journey makes Pre-Pay more expensive
than paper tickets for those journeys requiring a change of tram. When
capping comes along this anomaly is supposed to be corrected. We couldn't
figure out anyway this could be done unless time allowances are used in the
way you describe for a possible "through" bus fare in which case the 'abuse'
you describe would inevitably be possible. However I don't think we need to
consider it an 'abuse' at all. It sounds like a very attractive improvement
to the fare model to me.

(*) Why there is such a requirement is baffling of course when the Pre-Pay
card must carry just as much information as a printed ticket, yet just the
latter is accepted for through journeys. Clearly feeder buses might be an
issue, but not changes of tram.