This is ridiculous because we've spent decades moving in the opposite direction from being a country where a "citizen army" could realistically exist, or where an entire generation of young men could be conscripted into the military with barely a whimper.
To go back, society would need to become much more hard-nosed and would have to care far less about human rights, equality, and "touchy-feely" values.
None of this mental health or caring about feelings. If your MH is really bad, perhaps we'll put you in an asylum - otherwise you'll need your stiff upper lip as you keep calm and carry on all the way to the trenches.
We would have to become comfortable with the idea of citizens keeping and carrying weapons from age 16 upwards - not just knives but firearms - and being fully trained in how to use them.
And we'd have to go back to the idea of national pride and fighting for King and Country, so all the woke dogma and anti-Britain sentiment would be out of the window - indeed we'd probably have to imprison people for disseminating such dangerous ideas. To talk the country down in the way that people routinely do on here would be considered disloyal or even treasonous.
With an armed population, the risk of e.g. rogue militias staging an armed coup would be vastly greater so we'd have to get comfortable with having far less freedom to express political opinions and to organise politically.
Finally, if you want a world where men are conscripted but women are not, you'd have to erase decades of equality legislation and shift the compass back towards traditional gender roles.
None of this is realistic.