Coach
-a shower would be nice, one in each car.
-movie screens placed every few rows with no sound, you would need a headset or a Bluetooth device to listen in.
-a small "soundproof" lounge for parents to bring screaming kids or for telephone calls
-reserved ASSIGNED SEATS (PLEASE!)
Sleepers
-limited laundry service for bedrooms
-personal movie screens for videos and game rentals
-a box lunch option for meals (brought to room)
General
-wi-fi on all trains
-vendors that walked the aisles selling soft drinks, candy bars, sandwiches (sometimes it's the power of suggestion)
-onboard newsstand; can't tell you how many times I see people with puzzle books and wish I'd brought one; I thought the café car sold decks of cards years ago, they could expand on that with a few books/magazines.
I love these topics. It's always a neat intellectual discussion and back seat driving to determine what the passengers want vs what is cost effective and what can actually increase revenue.
More interesting yet (and has been brought up several times already in this thread) is what is wanted used to be, but is no longer.
Here are my thoughts on the OP's suggestions...
1) Showers. This is what makes Coach Class separate from Sleeper Class. Yes - when I first started riding Amtrak, I wanted the same - showers in Coach. However, the reduction of coach attendants (used to be one per car, now one per two cars if not fewer) are already stretched to the limit as far as their duties require. After all, they are effectively on duty non stop for up to three and a half days on some long Western routes. After all their other duties, cleaning a shower is probably the least of their desires. Some of 'em can't even keep the toilet functioning. Logistically there are other concerns. To hold enough potable water to serve around 70 passengers (1 per coach) or 140 (1 per two coaches) would add a tremendous amount of engineering to add, not to mention the addtion of the showerhead itself. It would also take away from revenue seating. IF this could all be resolved (speaking from an engineering viewpoint, ANYTHING can be overcome - at a price), you would end up having to charge to use it. Not a bad idea as it would reduce demand and increase revenue, but probably NEVER to the point of breaking even. SO, I believe that the current status quo of having a shower in each bedroom and a public shower for the few remaining roomette guests is plenty. An alternative that I have proposed is for private businesses to offer such amenities for a fee at large terminals, ie: LAX, CHI, NYP, BOS, SEA, etc.
2) This one has popped in and out for decades. After in-ride movies were discontinued in the Lounge because crews were pilfering videos and machines, there was an attempt by a private company to offer one-way DVD rentals. Think of it as a early version of Redbox, viewing machine included. This worked great for about a month (ok, maybe a bit longer, maybe never "great"). With the advent of affordable DVD machines - and more quickly, the advent of affordable laptops - this service was immediately obsoleted and it went away. This being said, I think ALL stations with an annual ridership of over 70,000 people should have a Redbox in their waiting room.
3) Not a bad idea to have a quiet lounge, but it's a matter of available space. This is just an aspect of life that we all deal with in different environments and in different ways. You don't want to go make your phone call in the room where a mom or dad took their crying baby, do ya? Which is more important? Maybe not for us to decide.
4) Yes - I've suggested for years that at least a coach or two on long distance trains be designated as reserved and seat assigned. Not all have to be, but a couple would be nice.
5) I don't think a laundry service would be that useful. The washing and drying time alone would be around 2 hours - last thing you want is to start a load and find out you're closer to your destination than previously thought. In the longest of cross countries, it's not out of reason to pack 5 days worth of clean clothes and still travel "light".
6) My case against corporate video goes for Sleepers as well as for coach.
7) Any sleeper pax can request any meal be brougt to them from the Diner. Heck, if available, same goes for coach - though they prefer to only assist those with disabilities.
8) I completely support WIFI on all trains, and I hope they can affordably bump up the bandwidth to allow streaming. Perhaps a paid-for option?
9) I have always wished that there were vendors/concessionaires that walked the aisles. However, the Hiawatha just got rid of that service, because the revenue from sales didn't even seem to offset by one penny the overhead labor cost. I would suggest what seems to be very successful in North Carolina - Vending machines.
10) I think this is a great idea. You know how many times I see bundles of newspapers sitting around intended for sleeper pax that never get distributed because someone doesn't get around to it? Sell them in the Cafe!
There are all kinds of improvements that can and should be made to Amtrak. However, if an idea isn't too expensive to implement, you could upset the duties of the crew.