It would lower liquidity, not add it! Say you have volume of 1M over 10 hours, extremely crude (most trading happens at open & close) average of 100k/h. Go to 24h, and that’s slightly less crudely (no open and close… probably most would now happen ~start & ~end of ‘typical’ work day, in the major regions trading in that market?) less than 50k/h.
You might offer more liquidity to a retail trader wanting to place an order for TSLA at 3am after discussing it on a night out (who currently can’t fill that instantly, and either leaves a limit/fill-kill order or places it whenever they wake up the next day, probably after opening) - but not to the professionals working whatever hours, who have the most volume to shift anyway.
Anyway, ‘theoretically’ yes, and it is something that gets discussed and tried - but not for liquidity. Another thing discussed and desired by some is much shorter opening; it’s that that would have the liquidity advantage, condensing all the trading in a day into just half an hour or whatever.