I support this! I think it would be useful exactly as-is, and...
Once a module IS set to "discontinued" here, I would love if you could tick a checkbox that says "Hey, I still want to buy this!", or something to that effect, which would flag that module with your unique user ID (must be logged in to see this new checkbox). This could serve multiple purposes; for example, the site could tally how many unique accounts indicate this option as a way to inform the manufacturer (or any would-be competitor) that there might be more demand for new production of the module than had been thought. This might give hope to a new production run in the future by the original manufacturer, or help to show that there is an unmet demand in the market for other companies who may wish to fill the gap with a similar module of their own. It could also be a way to collate data for private sales here on the ModularGrid Marketplace in order to inform the buyers automatically when the discontinued module they want comes up for sale. If this functionality already exists and I've missed it (which is possible, considering how powerful ModularGrid already is), then please ignore this.
Either way, I support Raccoonboy's idea.