i think this only fixes about half the issues with tera. forsure fairy and steel and water are very good defensive teras, and you get a lot of mileage out of even more niche teras such as tera ghost for the broken zama and dark on dondozo for kingambit. however i think you understate the damage just a stab tera can do; the recent suspect was at least 50% caused by people realizing that tera dragon outrage on gouging is incredibly busted since it both gets rid of its ground weaknesses and adds a water resistance and also allows it to brute force past things that should beat it such as garg or tusk.Banning Tera or more or so I mean limiting it to just the pokemon Tera'ing to ONLY its natural typing would probably resolve the Tera issue, cause most of the actual complaints I hear on Tera is because of resists/immunities the Pokémon gain when Tera'ng into lets say, idk Fairy or Steel and ppl wanted Megas gone and they stayed the psychological motto was cause ppl knew already what type the mon would be when it mega'd, it would only be the ability/movepool stab that got a mega banned
Not here to stoke a debate just a hot take I think would be logical
i think gouging exemplifies the main strengths of same-type tera in that it adjusts weaknesses into neutralities and allows brute forcing, but its not just gouging that could abuse it. Volc, for example, sometimes ran tera bug to get rid of the problematic ground neutrality and water weakness and get past tinglu and glowking at +1. Kyurem runs tera ice on specs and some dd sets to obliterate glowking. Gambit runs dark to obliterate that one 1400s stall team that hasn't figured out they need tera dark on dozo yet, etc. etc.
And if we did ban unnatural tera, the list would only grow. For example, one thing i've been using lately is tera fairy on valiant to shed its weakness to moonblast and brave bird from various sources, allowing it to beat things like moltres and corviknight easier in conjunction with encore + coverage while also making moonblast a nuke. Tera ghost ghold does similar things with tusk and moth, tera fairy prim heals to full with draining kiss, tera dark weavile can run band semi-viably thanks to not needing boots for rocks as much, etc.
also megas and tera aren't remotely comparable purely because tera can be applied to everything. if megas were a mechanic to add +100bst to any mon, it would be different, but as it is, megas can be tiered separately because they are only specific mons.