The below is based on an impression that you plan to mass-produce the clock.

But if everyone here says my pre-conceived idea is bad, wouldn't I be kind of stupid to continue to base my project on it?

Not the idea, the implementation and the place (see last 2 paragraphs)

for example:
develop by trial and error
basically never end with a reliable product.

for example:
you are concerned about battery life and have not posted anything in that respect beyond concern.

Whether e.g. the switches is a good or bad idea is NOT a subject for this forun, it is a subject for a "user group". I do not know how many "fantastic and wonderful" products never got off the starting gate, just because of a user interface the potential users did not like. You have made statements about what you do and do not like in a chess clock, you should drop all such. Get as many chess clock users as you can together, buy them a couple of drinks or whatever it takes to get them together and "design" the unit there. Then go home and do the electronics. As a reference we fly (OK, our product cost much more than a chess clock) our major customers in for a weekend of discussion before we start the design of a new model. a wild guess is that the design of the "player bar" easily can be a dealbreaker.

When you have the "what" together, come back here for the "how" and you can say "switches are mandatory" should so be the case

Erik