Belfast Switzerland Italy France London

Susan

Neither your post nor your profile say where you will be coming from.

Can we assume that you will have had several days in Belfast prior to D1, in order to recover from any jetlag and see some of Ireland and Northern Ireland?

Otherwise D1 you will be like a zombie.

Zurich is faster to Interlaken and if you want to see Lake Geneva as you travel through you will probably be asleep. Is there a reason you chose Geneva?

What time of year will this trip be?

You are gambling a lot depending on your one day in the Berner Oberland to be clear and cloud-free.

D5 another zombie day. Starts off well, will probably be lovely, I like that route very much, but I think you will start to drag after so many hours looking out through glass without moving.

D10 that's a lot of trains for a short day in the fabulous city of Venice - which deserves at least 3 full days. You may find that you arrive late so wind up being overcome by all the other tourists and tramping the same 5 percent of the city as them, and hating a lovely place. The way to see Venice is at sunrise and sunset, wandering off the main routes and finding your own Venice. At least leave Florence early in the morning and don't come back until late....

Yes, we will be in Northern Ireland a couple of days earlier. The reason we fly to Geneva is because there's no cheap flight from Belfast to Zurich and we would like to fly out first thing in the morning. There's nothing particular that we must see in Geneva. We will be travelling in Jun/July 2018 from Malaysia.

If weather doesn't permits for Berner Oberland, we'll probably go over to Bern and do some lake thingy.

I agree with you on D5! That's why I would like a suggestion whether we should do it or not. Or should I make a stop somewhere from Tirano?
Alternatively, D8 Rome - Venice, overnight in Venice; D9 Venice-Florence, 2 nights in Florence. Does this works better?

Very difficult in your time frame.
You will need to travel every other day.
Lucerne to Italy is a 2 day journey with Bernina Express.

D1 Belfast - Geneva - Interlaken (2 nights)
D2 Jungfraujoch excursion
D3 Interlaken - Bern - Lucerne (2 nights)
D4 Mt. Titlis excursion
D5 Lucerne - Chur - Tirano (via Bernina express)
D6 Tirano - Milan - Venice (2 nights)
D7 Venice
D8 Venice - Florence (2 nights)
D9 Florence
D10 Florence - Rome (2 nights)
D11 Rome
D12 Fly Rome - Paris (2 nights)
D13 Paris
D14 Eurostar Paris - London (4 nights)

In considering a rail pass, I would look only at the Swiss Travel Pass or the 2-country Select pass for Switzerland and Italy. The Milan-Paris night train is not covered by passes and the Eurostar coverage (with reservation fee) is not worth adding a third country to the pass (which will also force you to pay for 1st class).

A pass for 8 travel days of travel over a longer window in these two countries currently costs $390 per adult (age 28+), $373 per youth (12-27) and up to 2 kids (4-11) travel free with each paying adult. Coverage would be from arrival in Geneva to arrival in Milan. During your stays near Interlaken and Luzuern, you'll get 25-50% discounts on most lake boats and mountain trains and lifts. See more info on my Swiss link above.

However, I would prefer David's suggested itinerary, and that would need only 6 days if choosing a 2-country pass. It also reduces train travel distance and cost in Italy, making a pass for only Switzerland probably compare better. But the time period in Switzerland is 5 consecutive days and there isn't a closely-matched pass option, as either consecutive-day or flexi-day passes both jump from 4 days to 8 days and you do use counted days for the discounted benefits of this pass as well as transport that's fully covered. 8 consecutive days cost about $400 per adult (26+), $345 per youth (16-26), and free for all your own kids under 16. At the very least, if not buying a pass, then do buy a Swiss one-month Half Fare Card for $126 per person 16+.