@madis Welcome. You're correct. There are several people interested in contributing to the project, but Luke isn't quite ready to start managing code submissions to the core libs from a wide group just yet.
That being said, I think Modules are always welcome. Someone is working on a Markdown Module and we already have a couple of Modules by @caleb.
I'll be seeing Luke next week in person, so I'll pose your question to him and relay the response to you here in this topic thread, sometime around the 25th or so.
To my knowledge, there are a small handful of companies currently using Arachne or prototyping with it. So far, the feedback has been positive. It may be that Luke can only process a certain amount of feedback at a time during these early days. The project had over 400 Kickstarter backers, and I'm confident that Luke wants to present them with a cohesive initial design to reward them justly for their sponsorship of the project. As I understand it, the biggest remaining piece is Chimera, which you can read about in the 3 most recent ADRs, starting with ADR-015.
I do know that Luke does plans to open up the development to the community once certain milestones are reached. In the meantime, learning to write Modules will be a valuable skill to help wrap existing software, making it pluggable into the Arachne Framework. My lack of imagination regarding what to suggest has more to do with my inexperience with web development in general.
Perhaps a few of us could start meeting online and sharing Arachne knowledge and develop some best practices around Module authoring? Thank you for your candid feedback.