Hmm, LOL i never thought of that!!! In my case I have 5 fully built bases globally and I keep 8 soldiers in each base (40 soldiers total). Because those bases are widely and wisely spread, I do not need more than 2-3 hours to fly to the scene, clean the bugs and return. It never happened yet to attack my base while my soldiers are out in a 2 to 7 hour window.
Yeah, to be honest, I think since in 2.3 the aliens don't actually try to seize the base during base attacks (they usually just stand around outside), it probably wouldn't make any difference, but I try to play as if all the features are actually in place.
It could be handy to keep the lightly injured Soldiers (always take heavily injured soldiers in missions because when you heal them with medikit that is actually faster than hospital care) at bay for small missions unless there is a harvester-like attack.
OT, but the hospital vs. medkit thing bugs me. A lot of times I'll try to leave one alien alive so I can get everyone healed up before completing a mission. It seems backwards that you can heal faster with a medkit than a fully stocked hospital!
There is no need to attack a scout or fighter with more than 4-5 soldiers. The attacks in base use maximum 7-8 alliens and most of the times I have seen 5 attacking. So with 3 soldiers you should be fine and you could deal with them quickly in case they attack the base while your team is out on a mission.
Still by my experience it rarely happens. So keep 8 soldiers on each base but try to spread your bases across the globe for faster missions. Saves you game time as well.
True. The only other time it's a problem is when my firebird gets ambushed by a ufo on the way back from a mission and gets lost with all hands. But even that's rarely a problem because I'm almost certainly restoring from a save in that case.