Random question -

So my wife and I are doing our first "two-person" climb together on Eldorado Peak this week where we'll be going just ourselves with no other party members. We're going to be set up on a single 60m rope and will be carrying coils with the plan of defaulting to the canadian drop-loop for our primary means of extraction (vs. say a ZxC). My original reasoning for this was to allow for drag knots to assist in case of a fall, which would make the ZxC almost impossible to rachet out of. We're both religious bodybuilders and very strong, but regardless I outweigh her by a good 40lbs so I've figured it an additional level of safety (hmmmm, maybe I should have her carry more gear in order to even things out....).

So I was wondering, when you use drag knots, what do climbers do if they want to quick throw in a picket on a steep section of climb? I don't see it being too much of an issue for a climb like Eldorado other than the ridge just for an extra level of security, but I imagine it would be more or less impossible to get the knots through the carabiner attached to the sling of the picket.

Is that just the trade-off - you get some extra crevasse fall protection but forgo the use of running protection? You could find a safe spot, belay the other climber in and then untie the butterflies pretty easily if you saw you had a section you wanted to protect upcoming, but the logistics of that seem tenuous at best and prone to chance.

Is there some other way that I'm not thinking of?

I think you've already mostly answered your own question. There is no secret. It's a trade-off, like most other techniques.

Stopper knots do a great job of helping arrest an unexpected fall into a hidden crevasse (something most commonly found on easy to moderate glacier where terrain may not offer many clues). Generally, terrain that is steep or exposed enough to justify running pro is also the type of terrain that is very broken up (ice fall) or not glacier (just steep snow, rock, or ice). That's not always the case, but it comes down to protecting for the most likely or highest consequence outcome.

If you are on intermittently steep glacial terrain you can always take the knots out and put them back in. That should work out to about a 15 second delay each time you switch. Pretty reasonable.

You could run two lines between each of you. One with knots and one without knots.

I've done as norco17 suggested. One rope for drag and the other for rescue.