Spoke to my boss on this (vacations in Germany at least once a year)
and he recommended staying at vacation homes, these are called:
Ferienwohnung
These go at rates of US300-450 per week, yes, that's not a typo and
are available at all locations throughout Germany, from rural to urban.
They are essentially homes rented out by German residents to
vacationers.
Once the groupings are decided on Dec. 9th, the TT venue(s) will be known
and securing the above accomodation would be feasible.
Bless