There should not be too much of a problem doing this 

One idea here is have an event id field and use an SQL query - maybe using Simple Dynamic Dropdown, SD Databaser  or SQL Pack  (using an SQL COUNT query) and check how many of these event registrations are in the database, and if it reaches a certain number then the Submit button can be hidden using a conditional and/or a message displayed to this effect.

Yeah, that's a way. Nice idea.

That would mean a new table with registrants following the event ID structure, right?

There more I think about this, the more unnecessary work I fear will be involved in building a functional event system with Seblod. I do love the tought about tailoring the system to the exact need with Seblod, but it seems like a tremendous amount of work when I start to think about the system as a whole.

- You need to add events according to business specifications

- You need to manage registrants in an easy manner for the event holders

- Integrations towards other components to handle e-mails and reminders (I.E AcyMailing etc)

Hmm... but it sure would be nice, tough.. 

I would probably try to use two forms.

One to handle the events  [FORM A]

Event id (article id here might be fine), Event Date, Event Details, Event Price, Number of people allowed (max)

and another one to handle registrants [FORM B]

Event id (common field / related article?), Name, Email, Tel etc

So you list the events - people click on register [which has a parameter to pass through to form b and register]

I imagine with the code pack (or field 42?) and the correct php (afterstore)  you could pretty much add a registrant into Acymailing after completing the register form [Acymailing has API with all the relevant PHP code on their website]