Yeah post up a rough floor plan and ill see if I have any good ideas for you. sharing an en suite as said is a great idea if it will work in your situation
you said about light not getting to one area, depending on the building or layout you could use light tunnels to the roof, cheap and very effective
is this a renovation to rent/sell or your own house ?
yeah I've been doing this for years, dad owns a construction company and im studying as a civil engineer at the minute so hopefully can help you a bit