Hmmm. I'm beginning to see the point. This W/C will be ensuite to the
master bedroom so will only be used by myself and my wife. I know I
can resist the temptation to put anything other than pre-digested
material or toilet paper down it but I'm not sure about her.
As for running a shower and basin through the macerator, that is not an
essential requirement it just seemed to make sense rather than doubling
up the pipework. Your eloquent description of the drawbacks of this
have put me off this idea. Incidentally there are no plans (or space
for that matter) to put in a bath.
Without going into detail, the boxing in of pipes against the wall had
occured to me but are a non-starter in this case. I think my only
options are macerator, raise the floor or do without.

Thanks to all for advise so far.