Unfortunately, I think the only game in town these days for a single award ticket, is to take what united.com shows you. The same will be true for calling an agent. There may be programming to limit 24hr+ connections when searching for awards, but I wouldn't call it a "rule" around which someone can build an itinerary.

You could do a multi-city routing PHL/EWR-HNL and HNL-PNI, which will probably get you the times you want. Of course, you will be charged separately and likely higher than a single one-way between PHL/EWR and PNI.

I'd love to be proven wrong, but I think the days of customization, even if it sounds logical, are long-gone. Good luck.