I thought I did that?

Lets just do high level then:
Launch Tubes:
1) They need smaller internal storage than a full hangar (sure you will need a maintenance area for 20 fighters or so, but not 1 per craft). This is a change from the current tubes need full hangars.
2) They allow you to launch regardless of the ships Gs expended or evasion.
3) They allow you launch multiple craft per tube (lets say 10) per space combat round.
Hangars:
1) Significantly larger than the smaller internal storage required for tubes.
2) Launch can only accomplished when the following is not in use: evasion software, no pilot evasion
3) Craft take longer to launch. I dont agree with your preference that launching should "reasonable" - it should be unreasonable in ANY hasty scenario. This is the equivalent of you being moored - not on a catapult on a flat-top. That is the above.
4) A limit on the amount of hangars you can have - as each hangar is basically a very very large opening on the outside of the ship. That surface area is going to get eaten up quick. Perhaps hardpoint is a good indicator, perhaps not - but having 300 opening hangars on your hull has to mean something.
5) Something to do with hangars being destroyed when taking hull damage. Whether it is being more susceptible to critical hits or just losing them every X hull.
Simple. Hangars are not something you carry your fighters in except in well.. exceptional circumstances. It's something for a ship-boats, a shuttle, cargo shuttles, special ops craft, etc...
Of course you may prefer full-hangars to be much more useful in a combat scenarios, I would disagree with that. I want them to be near useless in a combat scenario.