Ceeway has some track ends with pugs (
here). And I'm pretty sure Nagasawa used track end with sockets but I don't know where you can get some of that kind. Like said above not only those ends have a given angle (I'm sure they can be changed a bit), you also have to deal with a narrow ID or OD range for the stays. I'm not sure I understand why you would need those.
Moreover, replacing drops is a job for the experienced. I've never done it (I've only build one frame), but it takes a lot of heat (heard many stories of people braking the stays in the process) and you have to be careful if you want to preserve the geometry of the bike.
So if the bike has standard foward-facing horizontal drops I would talk you out of it. They are perfect for SS/fixed, and are way more practical when removing the wheel for a flat (and for fenders if you go that way).
Otherwise you have the list of materials right. Apparently firebricks do help for this operation. But you'll need some know-how to make sure the slots are parallel, at the same height, same distance from the BB, etc., and to make sure you won't end up with a slightly slanted TT and/or different head angle.
It's really that hard? I might have to reconsider, as I've done nothing like this before. I mean, I've welded, but I figured that stock dropouts that weren't sockets already had slots in the stays...