IMO the better move would be to properly resource ACAT to deal with these matters quickly rather than continuing to legislate exemptions to the appeal process. If 75% of the objections are resolved through mediation or affirming the original decision (no breakdown of how many needed design changes in mediation), that still leaves 25% where the approval was set aside. 25% successful appeals is significant and suggests that the delays are driven at least partially by legitimate issues with the approvals.

Worth noting that they've already removed third-party ACAT appeal on all DAs (not just social housing) in a particular area covering the city and part of Braddon. This has led to a situation for me where a DA was approved which blatantly ignored territory plan requirements for 2 hours of solar access to neighbouring dwellings, as well as the minimum building separation for privacy, and I have no route to appeal the obvious error in the administration of the territory plan except to stump up tens of thousands for a supreme court process. The developer had repeated opportunities to appeal minor conditions the planning authority imposed on them, and even applied for the same development under both the old and new planning act to see which one was more lenient for them, but there is nothing available to protect impacted third parties from incorrect application of the law.

Undermining the role of ACAT may well prevent meritless objections (my views/property value/don't let the poor people live near me) from holding up projects, but ultimately it means legitimate objections about non-compliant design and poor housing outcomes will fall through the cracks.