Honestly I don't even think this improves the 5v5 aspect. I complete my item quest and suddenly I'm punished for doing it quickly? If I have to protect base as a support, alone, I'm punished by getting way less gold than I would have gotten. And it's not like there's any compensation what-so-ever from anything else. Gold from managing vision is very low. This will just incentivize killstealing as a support because every other player in the game can get gold from farm, while Supp can't. Sure we can go kill some jungle stuff but that'll piss the jungler off, who also has a scuffed brute-forced item that they must buy or else get no exp or gold at all.
This is a symptom of a long-lasting problem in League's design. Smite and support items. Back before the smite items existed people could technically go other summoners in the jungle, and as long as they could clear it healthy they'd be fine exp and gold wise. What they gave up was objective control and weakened themselves to invade and buff steals. Riot apparently saw a problem with that and brute-forced junglers to take smite every single game, by making the jungle income tied to a scuffed item.
Support items have been nerfed, changed, pushed around left and right because they've, since they entered the game, been extremely problematic.
The funneling was just a symptom of jungle items being weird. The no-cs top strat was a symptom of support items. Instead of fixing core issues they ruin the fun for everyone else. Funneling can be fixed without this approach. Ask yourself this, was it a problems that supports could farm items after they got their supp quest done? I bet you didn't think so. Letting the supp get farm should be a team decision, not a decision made by some arbitrary rules.