Then trading will be used only as "Save that resources", meanwhile major idea was to let players trade safe between all over the map?
I see your point and agree.
Some who run group limit servers (solo/duo/trio) sometimes feel trade allows players to work together above the size limit so while groups are limited to 3, teams of 3 can 'GIVE' each other resources easily. Being part of group1, I can give group2 C4 for cloth - or even nothing - effectively allowing 2 groups to work together and violate the group limit. So I guess trading is something to support, but it can support giving as well.
I was toying with the idea of limiting trade myself and then saw others were asking for something similar on another website.
My suggestion was to consider adding a configuration option something like this:
Restrict trading to team members: True/False