Showers Toilets and Sinks

[USA] east coast building code requires one of each for 8 people.
Is this reasonable proportion, or in reality it would be better to have more ?

The more toilets, showers, and sinks you can put in, the better it will be for your guests. If you have room for more than the code requires, then I would recommend putting them in.

www.sinkpositive.com have interesting gizmo which reduces significant amount of water.

The sinkpositive is a really cool idea. Do you think people would use it as a urinal though?

How difficult is to keep cleanliness if the toilet , and how problematic is the condition of the seat for people ?
Do they complain a lot , do they try to stand up on the seat the way is sometimes practiced in the east ?

We don't normally get complaints or have trouble keeping the toilets clean as long as our team checks them regularly. As far as people standing on the toilet seats, that would explain why ours need to be tightened and/or replaced so often. Maybe it happens a lot more than I would expect.

One of the possibility is the self cleaning toilet seat, but it would be expensive proposition.

We used to have the Sani Seats. The plastic covers sometimes got stuck and wouldn't turn right. The used covers also turned into a filthy disgusting mess inside the system. It's a great idea, but not so good for us in practice.

What about using temporary paper covers for the seat , how acceptable is that ?

The flushable paper toilet seat covers are pretty convenient. If your building has really old pipes, then they might not be able to handle the paper because it might clog the lines. With any modern plumbing setup they should be okay. A lot of people cover the seat with toilet paper anyway, don't they? The disposable covers would just make it easier.

But what about having multiple precleaned toilet seats stored on the shelf which could be placed and removed by the user ?
Of course latching mechanism got to be very simple.

I've never seen a shelf of pre-cleaned toilet seats that can be attached for each person. Is that a common system somewhere in the world, or is that your own idea?