So can you not do the bottle neck fix if you don't do a fuel return and new fuel filter?
The factor FPR is the bottleneck, so if you remove that you have to add an FPR. Technically the factory setup is a return as well, the fuel being returned just never leaves the tank.
If I understand your question correctly I believe the answer is - Since the bottle neck fix removes the pressure regulator in the tank you cannot perform this mod without a return line and external pressure regulator. The only 'filter' in the stock system is that pad looking thing attached to the bottom of the pump. Most people performing this mod are doing so because of fuel requirements for more power. So why take the chance not having a good filter and clogging up an injector or 2 thereby damaging the engine.
The factory FPR has a filter in it.