Make LG invite only, or something along those lines. If invite only make invites earn-able. i.e. ug bronze members get 3-5, silver 5-10, or earn-able through activity. Activity earning would be like UG bronze you get 2 for hitting bronze, 1 for every 25-30 non spam posts past that. silver would work similiarly but with easier/more gains.

OR

make non UG unable to do basically anything. people constantly mention scammers or other abusers of policy being members under UG status. simply move everything but general discussion boards, thus making it less easy for all of these problems to occur.

either method seems unlikely to happen, but the latter at least restricts access to important features while still allowing people to at least browse, and discuss, while not leeching, or scamming.