Hi
I am an Akeneo Developer and from the last 3.2 years I am working on it and I have created lots of the module to connect another eCommerce platform (Magento2, Virtuemart, Shopify, etc).
I can easily create a new connector for you to connect with Sylius where you can export data from Akeneo(attributes, category, products) the same way if you need then I will implement Import feature so that you can import your Sylius data inside Akeneo.
According to the feature delivery time may increase.
for more details you can contact also I am providing support of Akeneo.
Thanks