I think the sub band arrangement for very slow cw would be preferable to a
free for all.
Split frequency operation as well. Arrange for EU stations to transmit below
136 khz and the dx above 137.5 or reverse (EU tx  above 137.5 and dx tx 136
and below)
What ever arrangement suits most, as long as we all know what procedure is
in use.
The rest of the band to be used by the majority for normal cw. There could
also be a data mode sub band say 137.3 - 137.5 or there abouts.
With the use of so many high power FET rigs on the band the keying
characteristics need to be addressed to avoid clicks and sideband spurii.
Instead of keying the exciter into the PA, which seems to be the norm, the
PA supply voltage needs to be keyed and leave the drive on. Another
important consideration is a good narrow cw filter in the receiver and
preferably dsp. Some that complain about qrm is their own fault because of
inadequate rx selectivity filtering or a poor receiver. At busy periods we
all have to squeeze in and the necessary precautions must be taken.
A lot of LFers already know this but its surprising how many do not or rely
on luck.
G3KEV