The Swiss Travel Pass and the frequent trips on various lines give you a lot of flexibility. As you said, you can play it by ear.
The problem is that you are on one side of the lake, and Alpnachstad and Beckenried are on the other. That reduces the flexibility. That means that to "play it by ear.' which really works well on trains and buses in general, only really applies in a simple and clear fashion if you go back and forth through Luzern. You said that you do not want to do that. So,that introduces a bit of complexity.
I am sure you are confused by the flood of advice. I certainly was confused by all the options when I first started to travel around lake Lucerne...in i980.
And, if you are going to make it up as you go along, you need to be careful late in the day, or else you will likely have to go back through Luzern. So, writing down you trip options as you move through the day tells you just how flexible you can be.
Please consider this method. Please, please look at the map that I have been posting. Zoom it in and out. You'll get a feeling for what the schedules refer to. Even if you are not a map person, that will help you see what the routes are.
Zoom in and out.
Lay out a journey on a piece of paper with names of the intermediate stops..
For each leg, write down the probable times that you will take it and the arrival time at your destination for that leg. You might write down two or three options for the time you leave Alpnachstad and journey to Seelisberg.
Use the SBB timetable for that..it covers buses, trains and boats and cableways.
Skip the next step of the middle of the journey for the moment. Look at the end, so you don't get stuck.
Thus, write down all the times that the boat leaves for Weggis ( or Brunnen, as an option) from Treib. That is every hour at xx27 only until 1757. As late as 1834 to Brunnen; later on some days.
I got that from this Summer schedule:
www.lakelucerne.ch/fil eadmin/lakelucerne/con tent/Dokumente_Downloa ds_PDF/01_Fahrplan-Preise/01_Fahrplan/Sai sonaler_Fahrplan/2018/ 2018_Fahrplan_Sommer.p df
If you look on that schedule, you can see each boat route.
Now you can fill in the amount of time available between arriving at Seelisberg, including the taking the funicular down to Treib, and then catching the boat to Weggis from Treib.
In the later afternoon, in June, the funicular runs every 20 minutes
from Seelisberg to Treib at xx13, xx33, and xx53. less frequently
earlier in the day.
Within those time limits, you can be flexible. You have a lot of time unless you leave Alpnachstad after the early afternoon. So, get to Pilatus reasonably early, or skip the side trip to Seelisberg, and go Alpnachstad to Beckenried.
You can use the same kind procedure if you chose to go from Alpnachstad to Beckenried (use the SBB timetable) then Beckenried to Weggis. (Use the lake boat timetable for clarity). Faster than going through Seelisberg.
You'll have lots of time to do the route through Beckenried. You'll also have more than enough time to go through Seelisberg.
If your tabulation does not support this conclusion, let us know.
<<"Dec 10, 2017 - 11:09 PM in reply to Slowpoke
Thanks so much for your incredible help, RockOyster! It's a bit overwhelming at the moment and I'm more than a bit confused. There is a lot for me to digest here and to figure out regarding timetables, etc. but I will do so!">>
My handle is Slowpoke, not Rockoyster. I've never been to Tasmania. ;-)