I like a lot of the ideas mentioned, especially larger more complicated and detailed sets, Georgian buildings, an expanded Victorian theme, and a parts list for Specials. Unfortunately, however, I don't see any of this happening even though it very easily could. For example, I' be willing to pay an extra 10 cents or whatever it would cost to put in a parts list for Specials and I don't think that would affect sales whatsoever. Similarly, I'd be willing to spend $XXX on a huge, complicated, detailed set (e.g. a large pirate ship, a large medieval castle, a Roman town, a true Viking village, etc.). Although these obviously wouldn't sell well with children, Playmobil probably could sell enough to the adult and collector market, especially if they ran them as a "limited collector's edition of 1000 sets" or something to make it profitable.
Regarding pure figure sets, I think Playmobil is doing a mostly good job of this. For example, there are the 3-pack klickies and individual leader figures available for many themes, such as Romans, Gauls, various medieval groups, redcoats, Civil War, Western, etc. That said, there are a number of odd decisions they have made. For example, the redcoat package should consist of 3 identical privates rather than having one sergeant, one corporal, and one private. Similarly, when they did have the French bluecoat package, rather than having 3 identical privates, they gave us two different officers and one private. These poor choices makes it very difficult and expensive to build an army! With the Roman Add-Ons, while the legionaries, tribune, Gauls, and family are great, why don't they give us an archer 3-pack and why did they give the auxiliary soldiers the wrong footwear, helmets, and spears? (If the klickies are meant to be earlier legionaries then the pilum are okay.)
For my fantasy improvement, I'd like to be able to custom order klickies (e.g. body from A klickly in 1111, arms from B klicky in 2222, legs from C klicky in 3333, head from D klicky in 4444, hair from klicky E in 5555, beard from klicky F in 6666, epaulettes from klicky G in 7777, etc.). I know this would never happen, but it would be much cheaper and easier for those of us wanting to assemble customs by the dozens. Although this will never happen, if they charged enough per klicky and had a minimum order number, this could possibly make them money and make adult collectors happy.
