Just have them all train on a continual basis. Then make the barracks also be the entrance to your fortress, so all invaders need to go past the barracks.
While the new recruits will be unhappy at first, they will eventually tough it out. I find its easier to give everyone crossbows so they don't need to rely so much on melee combat. Instead, massed ranged firepower will do it. Sure, they may be very inaccurate at first, but the thing about crossbow bolts is that even if it misses the goblin they're shooting at it might hit the goblin behind their target. If you can funnel goblins in such a way that they're shooting into a green tide, even dabbling marksdwarves will never miss.
Get 40-50 of them all clumped up in the barracks and its a barrage of iron bolts that can take down even a dragon without much effort. They will rapidly skill up and become battle hardened soldiers.
You don't need any archery ranges. Don't bother with them. Just make a smallish barracks that has a good vantage point over goblins approaching the main gate of the fortress, so they can fire while on active/training. Between battles they will do individual combat training or conduct training exercises.
I've done this in my current fortress, resulting in exceptionally badass dwarves with 200+ kills to their names. Each. There are only 30 military dwarves in my fortress. I found that I just don't need 5 squads anymore. Even the 3 squads I currently have is hugely overkill. Once they become highly skilled with ranged weaponry and good with dodge/block I'll switch them out to a melee weapon. Every 5 years or so I switch them out to a new weapon type, going between crossbows, swords, axes, hammers, spears, and maces. My plan is for them to be masters of all weapons, but they start with crossbows.