> There's a reason senior engineers are paid what they're paid, and it's because it saves time like this

The right senior engineers, yes. The wrong ones, OTOH, would have gone further down the crazy path, inventing an all-new programming language and runtime for the server-distributed code (for 'security' or 'performance' or whatever other reason seemed to pass muster).

> They have a shop where designs are done in caffeinated weekend pushes without input from other developers.

I have a strict rule on my teams: no development outside of work hours (whatever 'work hours' means for an individual, where there are roughly 8 work hours in a day and five work days in a week). It is absolutely vital that developers get to recharge their mental batteries, in particular because a symptom of overwork is bad judgment, and a symptom of bad judgment is being less able to judge one's own decisions. Log out, go home (or walk away from one's desk), spend time with one's family: the work will still be here tomorrow, or Monday.