The buy land tool does not pay for a forge cost - that would make no sense and give no advantage to the player (why pay now what can be paid later?). It does not support dragging, but this would be a good thing to add one day in the future (any volunteers to code this?).
The ultimate solution would be a good thing to have indeed - but it has to wait in its own, very long, queue of higher priority tasks (unless anyone would like to code this sooner?).
Being able to build mothballed ways is not a good solution as it does not make any sense for a player to be able to build a way that cannot be used as such: it would be a confusing hack to solve a problem to which the concept of mothballed ways is not relevant.