I’ve worried about losing the yeast but I suppose its not doing much when its suspended in the krausen anyway, and by the time it drops the beer is almost done.
Getting rid of braunhefe might be more of an issue in a German pils or Munich helles.
I find that I’m using a blow off hose more often than I have in the past. It’s cheap insurance and easy to setup. My lagers don’t require the use of one, but most of my ales do. It primarily depends upon yeast strain, head space and fermentation temperature as to the need for one.
I do like the idea of fermenting in a carboy/BB with not a lot of head space, that would minimize oxidation without the need to transfer to secondary.
You shouldn’t need to worry about oxidation as long as you don’t open the fermentor frequently. The CO2 will drive off all the air. Secondary is meant to get the beer off of the yeast and actually adds to the chance of oxidation if not done correctly.
I know theres a protective layer of CO2 when things are actively fermenting, but this dissipates fairly quickly once no new gas is generated if the seal isn’t perfect. I haven’t had issues with yeast-derived off flavors, but I transfer to secondary before the fermentation is done to protect against oxidation when I’m brewing a delicate beer style.