Well, I'm not going to tell you what's good and bad for your business, but for what it's worth Ledger supports all of those things. Whether it's right for your business or not is up to you and your customers, but you're selling Ledger short by describing it as "hobbyist accounting".
Tax quotas, reverse charge taxation, the various date types, notes, links are all totally supported with Ledger's primitives as they are. SKR04 just looks like a list of account classifications, which is totally fine. You can either make that 1:1 with the account list you use, or you can tag entries in a transaction with metadata indicating that it's associated with that SKR04 classification.
Again, not attacking your decision to use your own format, it's the right choice in many situations. But ledger is literally the primitives of accounting – it's up to you to superimpose your system of rules and regulations on it, but since it's just double-entry accounting with metadata and tags, it almost certainly can.
Here's an example transaction, where somebody pays $20.00 for 20 tons of scrap metal, with links to the invoice, an invoice and transaction date, a mark to indicate that it's settled, and a $8 VAT liability that accrues at the end of the month.
2021-01-01=2021-01-03 * ACME Supplier
; invoice_num: 123
; invoice_link: https://invoices.widgetsandthings.de?id=123
; service_date: 2021-01-02
; notes: John said he'll charge us more next year.
Liabilities:CreditCards:Chase:XXXX $-20.00
Liabilities:Taxes:VAT $-8.00 ;[=2021/01/31]
; reverse charge tax, accrues at end of month
[Quotas:Tax:VAT] $8.00 ;[=2021/01/31]
; you'd use a "virtual" account to express "quotas" or "budgets".
Expenses:ScrapMetal $28.00
; I'm bundling the VAT and metal expense into a single entry.
; But if you wanted to record them separately, with their own effective dates, you can.
Assets:ScrapMetal 10 tons ; skr_code: SM2201 (I'm making this up)
Receivables:ScrapMetal -10 tons