It's certainly an intersting question. I'm a bit surprised how often Mass Effect is coming up in Destiny conversations, but its a good starting point, so why not? My thought is that it's hard enough to do progression in a single game, like Skyrim, really hard to do it across single player games, like Mass Effect, so it must be really dang hard to do it across presistent world online games.

One place to look is EVE Online. A world with lots of complex "abilities" and stats and so on. It's been running for a long time now and from my few months with the game it seemed that they had something of a handle on things. They seemed to be doing balancing all the time, mostly in large waves. With this update they'd introduce a group of new ships that were mostly balanced to the existing universe. The next they might rebalance an entire class of ships (small fighter like Frigates for example). One thing they did though was plan long term but implement in the shorter term. They would state that they were doing this, and this, and this in order to reposition this group of ships and abilities even if it took four updates over a year and a bit (but not a whole lot) of things going slightly out of balane in the mean time.

One other thing EVE Online did was hold chances for players to give feedback on proposed changes, and they held large scale tests to let users try out the new ships and systems and try to find any flaw that was overlooked. I'm not sure how much that really affected things, (I just played the game :p) but it seemed like a good idea. Maybe Bungie will be doing something similar? Constant balance updates with bigger features and storylines being added over time. Not sure how they'll handle Destiny 2 though as that seems to be a somewhat different issue than "simply" maintaining and updating an ongoing universe. EVE also has pratically no story, where I expect Destiny will have a much more involved one... maybe.

Anyway, it'll be something to watch. :)

How should legacy characters be handled in this new 10 year, multi-game franchise?

It is an interesting discussion. My curiosity of it stems from whether or not it will feel like a multi-game franchise or not. Given the structure put forth of Mainline games broken up by large DLC content with potential opportunity for smaller DLC in the interim, will we ever see progression really stop? Each game might have its own isolated expansion content (allowing you to continue to play through the main story bulk of earlier games) to allow it to be played even after direct support has ended.

I think the mass effect comparison is pretty apt for ways to deal with it, but another that comes to mind is the pen-and-paper Warhammer 40k Roleplaying system. The first 3 corebooks in that actually step up the power level (as is appropriate to the universe) of characters you create.

Assuming that the game has a large amount of gameplay impacting customization, and that it functions on a linear level system allowing legacy characters across all games (say 50 levels per game, total with expansion content) then perhaps newly made characters for each game would start at 50, 100, and 150 respectively. That allows for an even footing for all characters, progression-wise, with the obvious opportunity for carry-over gear for legacy characters. This could also be handled with a 50 from Destiny being equal to a 1 from Destiny 2.

I will admit, this suggested option would come off very strange if the core gameplay is not based around player ability but more on character ability, depending on how transparent the combat and stats are. Though I don't expect that to be the case. Additionally, how much customization comes to new characters after each game if it fits modern skill-tree-style character building could be abysmally daunting come Destiny 4 if they choose the route of full customization of new characters.

I am very interested in seeing how they choose to handle this, especially given their underscoring of each player being their own, unique character. Carryover seems like it would be important. But escalation for the sake of escalation has a high probability of making things unenjoyably complex. Which is obviously not the Bungie way. Well, except when we talk about the depth of their stories.

They talked a lot about customisation, and were also keen to mention the 'competitive multiplayer' aspect that is demanded of modern shooters. So I don't know if there is going to be a whole lot of 'powering up' your character over the course of the game - as that would obviously interfere greatly with the 'competitive' multiplayer.

I find the basic notion of "levelling" very frustrating.

I don't want to have my character hit for more damage because they got to some level by grinding through levels or got a sweet loot drop.

I want my character to hit for more damage because I got better at targeting or if it's because of a sweet loot drop I want there to be downsides to the loot such as slower movement/reloading.

If it all worked that way, you could keep all your customization through each game without having to worry about it. And yeah it's tough to balance things, that's a part of good game design.

At its best, you don't play through each halo game picking up progressively more powerful guns and never touching others. You move through the game picking up weapons based off the given situation and what strengths the weapons have in that context.

Now if Destiny ends up having Levelling, I will deal with the frustration of being slightly off-level from my friends and the hollow satisfaction of doing more damage with the same character to the same enemy because I've simply been playing longer. I just hope it doesn't go that route.

And I guess that's mostly what we should be doing here... hoping.