Better multilayer support

[!i!]

Hi there, by usign JOSM to migrate a huge amount of buildings to OSM (see ​http://wiki.openstreetmap.org/wiki/Rostock#Geb.C3.A4udeumrisse_des_Katasteramts) I noticed that the multi OSM layer support in JOSM is quite poor supported.

So what would be usefull?
-"send to layer n" function to copy it to the exactly same area
-import a smaller area of the .osm file -> we can break down work
-copy only new attributes -> e.g. source wouldn't be replaced
-simple drawing e.g. bounding boxes for zoom/panning view -> no slow down for huge amount of detailed objects

for further contact please see ​http://wiki.openstreetmap.org/wiki/User:%21i%21

[Gubaer]

Since r1890 there is "merge selected" actio. It "merges" currently selected primities to any other layer.