gold issues on supports
I think the big way to make supports more powerful is by putting their power into somewhere that other classes won't get... so either assists, gp5 items, masteries, or a combination of them
imagine there is a mastery that makes gp5 items give way more gp5 and then they lower the base for them and gut the stats on them
imagine they make a talent that gives you 10x your gp5 for 10 seconds (to make beating your opponent grant you gold)
an alternative would be to have assists give a support 100-200 extra gold
another possibility is to give either static or scaled gp5 after so long of not killing a minion creep (still not matching lane csing though or else supports would never want to cs)
I think the fact that supports use gp5 runes and masteries, mostly go for assists, and use support masteries, those would be the best places to put their gold. putting them anywhere else makes no sense. but overall I don't see any major changes needing to be made to how the game plays, just minor adjustments to how things that normally don't give much gold affect supports...
p.s. the most important thing is to make sure the gold you get as a support is acheived from good play, and is NOT given for free
tl;dr- put extra gold in either assists or masteries and possibly that scale with passive gp5 so that suports with their support masteries and gp5 runes can take best advantage of them.