Well, there's two major problems with this. Instead of cooler oil from the bottom of the tank going to the engine hot oil would be circulated. Also, when the engine is shut down, the oil would be siphoned from the tank to the crankcase as there's no check ball in the return pump.
The first question about siphoning is now solved I think? at least it is now known that there should be a hole for relief. Next thing i see here is the "circulate only hot oil part"
Although your method of thinking is correct, there are more factors at play here. you should take into account that the hot oil is actually passed from the fron to the rear, thus cooling itself and heating the other oil in the process.
Also imagine this: You just starter your engine, your engine is spewing out boiling hot oil, while at the feedside the oil is still cold and thick. It will have problems with getting enough oil when the engine is cold if the return pipe would just end in the front.
If you have issues with leaking trhough the return pipe there is 2 possibilities basically:
1: oil level to high, blocking relief hole or blocked relief hole by something else
2 leakage in the oilline after the reliefhole
This is what I think, but most likely some of the more experienced drivers have seen many other causes..