v3 SDK feature requests

### Problem

There may be some feature requests that will require a new version of the SDKs. This issue will capture the feature requests that should be taken into consideration when creating the next version of the SDK.

### Solution

Captures the feature requests in this issue.

**Features**

- [ ] The transaction fee payer (client operator) should be able to support a multi key account
- [ ] The SDK should represent the Hedera network as whole offering a complete experience between the different products and services
- Includes mirror node rest API support, JSON-RPC relay, local node etc
- [ ] Operator ID is a strange name to use for an account that we specify to pay for transaction fees. This should be named something like transaction fee payer that is more intuitive for the developer to understand what this is

### Alternatives

_No response_