If we have a flu that is as dangerous to kids as the 1918 flu? I would absolutely support a flu shot mandate for schools.
Did you think 1918/1919 was just an ordinary bad flu year? It killed three times as many people as World War 1.
As to kids, flu kills more of them than COVID does. So it's the sheer number of people you worry about? Presumably then, if the IFR for the omicron does indeed (yeah I know...early...wait for the UK...there's also some interest data that because it attacks the bronchi more efficiently than the lungs it might also take longer to hit critical) falls to the level of the flu, and everyone catches the omicron (for which vaccine deployment will be too late), the need then for a COVID vaccine would no longer exist if 100,000 elderly people die every year from it and its just endemic? 28,000 died in the moderate flu year of 2018 (sometimes the number can hit for the US as high or over 50,000). Your argument for vaccines then is "yeah you might have to take 4 or more but eventually it becomes optional once the numbers aren't as high?"