So ... : I now declare the bazaar open
for speculations of what might be 😁
The Luxembourg expansion angle is interesting. Add Longwy to it as well, and Liege. Elevate the Duke to a King, incorporate it into Germany, maybe it makes it more palatable to the French speakers, and to the Luxembourgers.
... but ... who or what authority should enact such 'elevation' as there isn't any accepted as by the at least european nobility anymore.
A Grand-Duchy as Luxembourg already was - and still is - would suffice completly. There were already a numvber of such being members of the German Realm Luxembourg very likely would be invited to become a full member (not only part of the german custom zone it also already was).
"Simply" adding the iron region to Luxembourg ... as I said above would have - and did cause IOTL - some lagalistic comncerns. Even in OTL Bethmann-Hollweg painstakingly looked at NOT requisitioning french or belgian or luxemburgish industrial holds and interests but installed a trusteeship over them. ... not seldom much to the regret of german industrialists not already engaged in this region and the similar far-aways of the political Ludendorff biotope.
As
@DUWANG has proposed: much more than arrondissement of Arlon or ... "Arelerland" what even
ol' Paul Eyschen might have 'accepted' but nothing more) I wouldn't render sensible. All these further annexations of/from Belgium are part of the as well already mention (unrealistic) wish-dreams by the uneducated that floated around in germany.
..., as colonies for Germany were a fiscal drain ...
... well ... this for political correctness again and again stated and due to unconnectedness to context IMHO myth esp. regarding its intent to 'demonize' colonial holding even in the political context of its time (
but who asks for timely context if we're today prepresent the pinnacle of human ethical development all around giving us the right to judge morally over times gone ...) somewhat lacks in ... contextuality.
In absolute numbers the statement of "colonies cost money and don't bring any" - ofc without looking at i.e. trade and sales volumes, buisness gains with processed produkts - isn't completly wrong. ... aside german Togo and german Samoa which wiggled around breakeven since about 1910.
However, let's even stay with these numbers as raised looking at the development.
While in 1904 the expenditure of the german colonies overall stood at ~ 745 % of their income this relation steadily declined in 1913 to ~ 158 %.
Even the ONE TRUE sink hole of money - Kiautschou - starting in 1904 with expenditures or 13.5 million RM and an 'income' of only 0,91 million RM (former being only short of 15 times the income) this develeoped to16.8 million RM expenditure in 1913 by an income of 8,06 having declined to barly above 2 times the income.
This seems to me to be a rather 'promising' development esp if one acknowledges the often named (or complained ?) rather un(der)developed exploitation in processing and commercializing of the colonial holdings and their resources.
... Longwy is worth way more than any colony.
As I admitt that the Longwy region might be esp. faster to bring profit (
if in the end ... over some time/few decades ... more ... might be challangeable) it would add much less regarding prestige and esp. global political 'weight'.
Contrary to todays perception by many and esp. and unfortunatly by politicians as well of poltics (
at least until there came Xi and Putin ... though there are still enough of the bunch NOT acknoledging the raw will and wish for power only of the two) as anything but improving economical profiteering only at the time in questionabove mentioned topics were (still) more important than quick profits for a few.