Noratlas could have wingtip(?) mounted jet pods.
C-119 could have a dorsal jet pod.
Bronco could have a dorsal jet pod for target-towing.
Shackleton Mk.3s had Viper turbojets in the outer engine pods.
Neptune could have underwing jet pods.
Re the Wellesley/Wellington debate, you could always go the other way and attach the Wellesley kit's spare engine to the front of a Wimpy, then add a gondola for the bomb-aimer.
How about adding a third, pusher engine to the back of the fuselage pod on a twin-boom, twin-engined design? The P-38 is probably a bit too small (maybe a small jet..?) but the P-61 seems ripe for it, as does the Fw-189.