They _should_ have the corp version. Corp accounts (@corp_name) should be like $1000/year or something like that (probably could charge $10,000 and more). Nike, Coke, Dell, Disney, etc.
You know — that is a genuinely good idea. It's easily the best monetization idea for Twitter I've heard, especially amidst the last decade of nonsense about "brand advertising" and "blue checkmarks."
Just one thing — add a couple more zeros. $100k/yr is not unreasonable for an enterprise offering here. They could introduce all kinds of B2B features for companies that want to use Twitter as a support forum (or, given Twitter's popularity, are forced into using it as a support forum).
Off the top of my head — things like rolling up different sub-accounts under one main corporate account, formalizing the ability for multiple support staff to work one account (and charge per seat!), having deeper integration with Zendesk and other ticketing systems, extracting metrics and showing dashboards for how support (and sentiment) is doing, introducing some AI/ML to help companies match Twitter accounts of their customers to internal customer IDs, enabling ML-powered DMing of targeted offers, introducing chatbots that can be trained to field support queries over DM, etc, etc.
Anyway, it's a really good idea. Maybe you should've bought Twitter.
Basically a tier for global brands that manage multiple regional accounts and need top level support. Which I'm sure already exists informally like all B2B SaaS sites that have listed monthly fees where big accounts are handled personally.
But more to your point I think there should be a paid bracket below that tier of global mega corps which is formalized and public. At least for transparency and marketing reasons.