那家 airline 可包辦以下行程

Agree these are too short a hop to do by plane. You wasted too much time travelling to the airport, check-in, and wait for the plane.
Innsbruck - Florence - Paris can easily be done by night train.
For schedule, can try: http://reiseauskunft.bahn.de/bin/query.exe/en

My recommendation will be
1. Fly into Munich from HK via Lufthansa.
2. Take a train (2-hour) into Innsbruck.
3. Take a train from Innsbruck to Florence (6-hour overnight).
4. Take a train from Florence to Paris (14-hour overnight).
5. Fly back to hong Kong from paris on Lufthansa via Frankfurt or Munich.

So basically you buy an open-jaw air tickets. HKG-MUC and than CDG-HKG, or buy a HKG-MUC-HKG roundtrip than a separate one way CDG-MUC. Depends what's cheaper.

Hope this helps.

如果你要每一程都飛機既, 就一定有好大難度...
如果你接受到火車既, 你可以選擇 air france. 由香港飛巴黎, 轉機去佛羅倫斯. 然後係意大利買一張來回奧地利 innsbruck 的火車票 (車程 6 小時多, 一晚到), 玩完後, 係 innsbruck 返佛羅倫斯, 飛回巴黎 stay behind, 玩完再返香港
如果你堅持全部飛機, 一樣, air france 來回巴黎, 轉機佛羅倫斯. 然後搵香港旅行社買一張由佛羅倫斯的來回維也納機票吧... 因為佛羅倫斯沒有飛機去 innsbruck 的... 到了維也納後, 轉火車到 innsbruck 吧...
相信沒有套票了... 建議向旅行社查詢一下, 因為比較複雜, 始終我們也不是專業的...