Upgrades / Downgrades have been planned for some time, but I couldn't find the task either so I've assigned it to CORE-1127 which is planned for 3.3. Price overrides belong to CORE-747, and a mass mailer is assigned to CORE-621.
We know there are some features that are holding people back from fully embracing Blesta and those features have the highest priority.
We think people are really going to like 3.2 with the new responsive bootstrap client area, new order forms, new ticket system features and a lot more. We'll build on that in 3.3 with upgrades/downgrades, proration, proforma invoices, etc.