The publishing possibilities shown in the new communication sites serve a great insight of possibilities to create content in SharePoint. While this is an suitable approach for user generated content such as in Wikis there is a high demand to provide a consistent corporate wide communication.
In the past this was possible through page layout option which is now missing and removes the ability for corporate communication departments to manage, plan and organise the content to communicate.
In addition the missing page layout option lead to inconsistent and at least time consuming page creation. It will be hard to recreate the same page again because all asset types and content elements needs to be placed in the exact same order on the new page.From previous project mostly two to three page layout where enough to provide an efficient way to create and orchestrate content creation with enough flexibility. The current page variant selection is not an appropriate equivalent.

The current communication site template cannot be used for corporate wide communication because there are some important things missing.
The overall design is only able to speak and represent only the Microsofot CI/CD. The missing branding and theming options makes it hard to be used in corporates because there is currently no way to apply corporate communication and design guidelines to the page. For user it makes it hard to identify the page as an official communication channel by the company and not by Microsoft.

In addition not even well known and supported customisations through Themes is possible at the moment to change the look and feel. Changes in themes does not reflect in the communication site at all.

Overall it is hard to sell the communication site to marketing and CEO from a customer prespective. Right now the only valid option to establish communication channels at customers is through the classical publishing features (with not such a fancy page creation) or through classical blogs.

The flexibility of page creation mostly will overwelm business users and is definitly not markting and communications departments like to have. There goal is to provide fast and effiecent information. Right not the community portal lacks of two things:
1) Consistency - Any user can create any layout and it will be hard, time consuming and inefficient to create a consitent layout
2) Missing metadata for further filtering and content categorisation
3) No branding options to speak the tone and voice of the companyThis is the most challenging piece of inconsitent communication because it doesn't allow to speak the voice and tone of the customer it is only a well crafted application in Office 365.
Because of the last bullet point here customer already search for alternative intranets and communication medias to represent the corporate CI/CD Guidelines and go back to tools such as Wordpress. This is the most worring part because SharePoint in the past was always a good intranet content management system. Improvable but working.The first step to fix these issues will be to have custom page templates that allows to create new content structured fast and efficient with fixed content block. Metadata to categorize content and avoid to have multiple comminucations sites that user need to look up.
Finally branding made SharePoint huge and was always a great selling point to marketing, beside the collaboration aspect, ECM and other aspects. Right now it feels like writing a corporate word document and be only allowed to use the default template with only the ability to add a custom logo.

Can you consider making the out of the box communication site SPFX web parts open source to allow the community to modify their functionality and install them as per SPFX?

In Comm Sites, some the new web parts are basic or provide little no editing capability or to enhance them to incorporate the edge cases where a organisation needs to tweak the web parts accordingly.

At the moment, they are a great starting point to get comm sites up and running but a open source version will allow developers to take what you have built and enhance/change them to meet specific requirements whilst reducing the amount of re-inventing the wheel.

For security protection, I am considering to restrict the creation of the Communication site by general users. However, I have received the guidance from the support desk that the Office 365 group will also be the same setting when controlling the creation of the Communication site in conjunction with each other by default behaivor.

Therefore, I hope the feature will be improved to allow general users to create Office 365 groups only, therefore, it would be useful if the feature will be allowed separately controlling the creation settings between the Communication site and Office 365 as well. Thank you for your support.