Implementing DKIM and BIMI with Exchange 2016

Hi,
My customer wants to implement BIMI.
His environment is composed of an exchange server 2016.
To receive and send mail he uses a provider as a smarthost that also acts as an antispam.
From what I read in order to implement BIMI, SPF, DKIM and DMARC must be configured correctly.
The spf record is already configured correctly.
For the DKIM issue, the configuration must be done by the provider and then I will insert the dns record with the correct parameters in the public area.
Once the DKIM is configured, I can configure the DMARC by creating the dns record in the public area.
My first question is:
If the provider does not support DKIM, is it possible to install a third-party solution and then continue to use the provider as a smarthost?
My second question is:
I imagine that exchange does not natively support BIMI, since it does not even support dkim. In my configuration the BIMI service must be implemented by the smarthost (provider)?

Thanks