You should be able to book these self-constructed routings on a single ticket yourself using multi-city search. No need to go through an agent. For awhile, they were blocking multi-city bookings with layovers less than 4 hours, but they have since reopened this ability. There shouldn't be any need to check-in twice or re-check luggage with such bookings. They will generally cost more than single fare bookings on a route (since you are booking two fares), but they can't really prevent you from doing this. In the end, the revenue is the same as if they booked two different people on the two fares separately. So they shouldn't really care.