It might have been more dramatic if these characters had recurred several times and then she had die ultimately. "Real Life" would have progressed as it did, except instead of death, he could learn to treat his kids like people, not just re-program them to do what he wanted. He could have mentioned his kids and wife occasionally in other episodes ("Now Belle wants to be a ____. Last week, she wanted to be a ___." "We're having dinner with the Martins again. I like him, but I can't stand that wife of his. She's always talking about her cats." "I have to go to a PTA meeting at Jeffrey's school tonight. Charlene volunteered me to help set up booths for the spring carnival.") Things would be said to him like "At least you can turn off your family when you need to, make a plan for what to do, and go back to the program." When Belle does die, it could have been later in the series, around when they have contact with Earth, and via Pathfinder, etc, Barclay could set up a meeting with Deanna Troi for him to decide whether or not to feel/experience it. If this happened just after Lineage, Torres telling him not to change the program would be more poignant, as she can draw on her decision not to change Miral's DNA to be less Klingon to advise him not to skip Belle's death, or if before Lineage, he could have pointed to this to advise her.
The thing is that unlike Fair Haven and Captain Proton, which are clearly fictional lives they can't live without the holodeck, The Doctor is attempting to live a kind of life that he could live on Earth.