Day 4 is a good trip, but the ferry portion takes 3 hours--you might not get back in time. You might consider not doing the ferry.
One of the possible routes I noted was Luzern to Locarno goes through the Gotthard tunnel; before reaching the tunnel, the train spirals around the Wassen church, you first see the church on the left below you, then on the right at eye level and then from above on the level; this route is part of the model railway in the Swiss Transport museum on the outskirts of Luzern.
PS: second class seating (except during rush hours) is very comfortable in Switz., so if money is a problem, buying a 2nd class Swiss Pass is an option to consider. On virtually all mainline trains, there are lots of coaches, some even double decked.
Have a wonderful trip.
thanks a ton for the help nrr... I will definetely take all ur feedback into consideration and then make a final itinerary.. will share with u again for ur valuable final advice.. cant tell u how happy I am to be in FT and get in touch with ppl like u, who are more than willing to share their deep knowledge ..^