Enabling Print Settings->Infill->Reducing print time->Combine infill every X layers has the effect you described. Here's the setting:

The limitation is that your combined infill layer heights are still limited to 80% of the nozzle size or less to ensure good adhesion. Any higher and extrusions will have a round cross-section that doesn't provide as much surface area to adhere to adjacent layers. This in turn limits your external perimeter heights to a fraction of that. With a 0.4mm nozzle, your infill could be printed at 0.32mm but your outer perimeters are limited to 0.16mm (assuming you want nice even multiples). If you want to use combine more than 2 infill layers, the perimeter heights drop proportionally. This has the effect of increasing overall print times as you're reducing layer heights, then offsetting that somewhat with this strategy.

Here's what it looks like in action:

It's not a bad idea, and I don't meant to be discouraging. The time gains aren't particularly worthwhile in my experience. A 40mm cube that normally prints in ~1h33m drops to ~1h27m in the slicer estimate. These are usually close.

Oddly enough, this is the 3rd time I've seen someone with a "super fantastic idea" turn out to be exactly this same feature once they explain it. Don't feel hesitant about suggesting and discussing these sorts of topics. There's a wide user base with a lot of deep experience here that is happy to kick around ideas. When you get a good one, posting it up on the GitHub pages is your best bet.

The idea is to use say a .2 nozzle (should scale up as well to .4 etc) and rather than print the entire layer at the same height, have the outer walls print twice at .1 building a smooth shell that is .2 in height

Then have the infil go in and fill at .2 (or if using a .4 have infil at full height).

I cannot see how it would cause issues for the print head as the way I see it the infill would be no different than if the outer skin was printed at .2 in the first place.

It would be interesting to see how it affected the print time of a larger object using a .8 nozzle with outer walls printed at .2

I know the slicer has variable layer heights already but that still prints the entire layers at the choose height.

Let me know what you think? 

Shane

I am not sure about posting it up on here as it could be a game changer and would hope that it might get some recognition, or atleast cool bragging rights with my kids lol.

Do any of the Devs frequent the forum? Would love to run it by one and see where it goes.

Fingers crossed they will agree it's cool and one day soon it could become a feature.

Hope to hear from a dev or interested party soon.

Shane