What I call currency brokers : TransferWise, WorldFirst, CurrencyFair and the likes

At InteractiveBrokers, you could deposit in EUR, convert to another currency balance (at a very competitive rate, above ut the Transferwise around the mid market interbank rate) without taking a speculative trade, say in USD, then withdraw these mint USD to your bank account.

Most retail FX specialised brokers don’t offer the possibility to switch of base currency, or forbid to withdraw in another currency than the initial deposit one.

Are you aware of other brokers that would work the same than IB ? Or even white labels of IB (IB has inactivity fees)

NapoleonDynamite 

At InteractiveBrokers, you could deposit in EUR, convert to another currency balance (at a very competitive rate, above ut the Transferwise around the mid market interbank rate) without taking a speculative trade, say in USD, then withdraw these mint USD to your bank account. Most retail FX specialised brokers don’t offer the possibility to switch of base currency, or forbid to withdraw in another currency than the initial deposit one.

Are you sure? I tried to do this 2 years ago, wanted to change a sizable chunk of GBP to USD and was told that they would not except an incoming wire not denominated in USD. (I'm obviously a US client.).

Yes, they even put in place the minimum commissions on FX to discourage those using IB as a bank account (statement from a support representative)

Dukascopy do that