This is the current default.
I think the important part here is that users are notified of pending updates, and then get the option to postpone them. I think very few users will remember to go into settings and postpone all updates until after their big presentation. However, if a user has a big presentation the next day and they get a dialog asking to run updates, they might say “postpone them until after my presentation”.
So in short, snapd should warn desktop users that an update will happen and give them an option to postpone updates then and there.
Holding updates on metered connections is already possible, see Keeping Snaps Up To Date.