Bike travel bags, hard cases, and homemade bags I am regularly using airplanes for transportation
between race destinations. In fact, travelling with
a bike is always a very stressful situation. Usually, I am
very afraid when I have stopovers, because most
of the airport staff do not handle my bike bags 
politely. In line with this, when we arrive on
final destination, bag is very dirty and some
parts are even broken or damaged. Despite of many
bags that I have already used, I am wondering if
there is a possibility to create a bag at home.

Has anyone experience with homemade bags?

I am still looking for appropriate material. Wood
seems to be very heavy, whilst cardboard boxes are
too soft.

What do you think?
If you travel regularly, buy a decent, high quality hard shell or accept your bike will be damaged. Even with the very best case, your bike could be damaged - either accept it as a cost of travel, or purchase travel insurance that covers the bike. 

Depending on your travel and carriers, you will probably find a home made case will offer poorer protection and cost more in baggage charges due to it being heavier. Its unlikely a home build case can be made light and strong compared to a commercial hard shell.

Also consider the cost of a damaged bike is may be far more than the cost of repairs. If you bike is badly damaged going to your destination, your entire holiday could be ruined. Travel insurance can help here as you would not need to be concerned about cost of repairs at destination (e.g. say you bend a derailleur and the only available replacement at the bike shop is Ultegra or XTR, insurance would cover the repair cost).