No pod at all would be by far the best option. The whole point is that if there's nothing to hit solid water then there's nothing that'll slow the boat down. Water is a far harsher mistress than air in this regard as I'm sure you know. Just look at how small and simple it is to produce a brake for a hydroplane.

BUT... there's always a "but" isn't there..... life is all about compromises. Without a center pod to sit the crankcase or magnet bell of the engine or motor into you may end up with a drive shaft angle that is way too steep to work well. In my very limited RC racing boat knowledge I'm seeing that pod as a way to clear the engine crankcase to optimize the prop shaft angle. The other option may be to use a universal joint down near the prop shaft support to slightly alter the angle. Then it becomes a tradeoff between the engergy sucked away by the crankcase pod hitting the odd bit of solid water and the mechanical drag of the universal joint. A typical universal joint such as used on model boats used to even slightly "bend" the power line produces a HUGE amount of drag on the engine. The key is to find the best single or combo of design traits that balances all the needs.

And as you've seen from all the solutions from various boat makers it's not an easy set of factors to balance out.