I'm always grateful when a producer includes several different style spare heads in a set. Especially when the heads have a long peg connecting it to the sprew. This way it can be cut close to the sprew and as mentioned, drilling a new hole and just pushing the peg into the shoulders is tight enough. I use isopropil alcohol to lube it so it goes into the hol more easily. When the head is a "snug" fit Swoppet Style there is no need for glue.
I also aprreciate extra heads included in each set because the colour is the same since I don't paint my collection.
I love doing conversions and always swop at least some of the heads, so Roger W's idea is a great one.
I think it is a fantastic idea! I have been meaning to ask if Strelets would consider selling half sets of some of the superb new Napoleonic Russian figures: all the men wearing overcoats and forage caps work very nicely for Crimean war regiments, but I don't really want to buy a box of figures if I can only use half of them. A box of heads with forage caps and spiked helmets would be just the ticket!
Heads with slouch hats would also convert the excellent Boer War British into late war, as well as the obvious ACW opportunities