Keeping the same protagonist in MEA games?

Bioware people already said that Andromeda is not a trilogy or series, every game's story starts and ends and so the protagnist's story starts and ends
so they won't keep the same protagonist

Don't care. Honestly still a little upset we never got a spinoff game where we play as Garrus during his time as Archangel. If not being locked into the same protagonist(s) allows for something like this to happen, then I'm all for it.

The spinoff you describe wouldn't be a full standalone game, but rather a smaller add-on that expands the universe like Leliana's Song. 

I want this so bad now. 

That's not what they meant, exactly.
They talked about story arcs. They said we will have a complete story arc each games. You can do that with the same protagonist or not.
Think about a TV series with that pattern. All I can remember is Fringe:
Each season of Fringe was planned with a season mystery revealed at the end of the season. In addition, the end of the season planted some other new mysteries. If the show was cancel, you could have thought the series have an end. If the show would have keep for another season, you have the new mysteries planted before.

Edit: Of course, by the end of the season 3 we have a consistent mythology of the show, the characters and their backstories. No season was isolated from the others.
The key part is having something autoconclusive just in case.

Same protagonist means we get to know the companion more, which is always good. We can see events shape their personality on longer span of time.

So were Mass Relays. 

The same protagonist is fine. It would be nice if the same writers wrote each installment for story consistency. Also, non of this "This second installment is a great place to start" nonsense.

Here's the rub: development on sequels doesn't start after a game releases. In fact, I'd say pre-production is currently happening on the next Mass Effect, and deciding on a protagonist is something you'd definitely figure out at the very start of pre-production. How is BioWare going to know how well everyone takes to Ryder before their game comes out? Sure, BioWare have testers giving constant feedback, but presumably, you want the arbiters of Ryder's quality to be us, not people internal to EA.

More importantly, what does "great" mean in this context? I can easily conceptualize how a bad protagonist could get weeded out, but as a AAA developer know for their writing, I can't imagine BioWare would put out a plain bad protagonist. It's the one character that's always around; if they're testing that poorly, you'd know. The worst case scenario is that we get an uninspired protagonist. Someone who works well enough, but won't knock your socks off. Even if they're not a "great" protagonist, I doubt anyone would complain enough to get BioWare to fix it.

Regardless, I feel like having the extra character development should be a non-issue. Obviously, more screen time means more development (provided we have writers who care), but we shouldn't need a second game just to properly explore a character. If Miranda was lame in ME2, either it's your fault for not exploring the depths of her character or it's BioWare's for not putting any depth there to begin with (or not convincing you that the depth is there). We shouldn't need another game to make her character arc to be complete and we especially shouldn't need it to make her character the least bit enticing. Sure, it's great to see a character grow further in subsequent games, particularly in the new narrative context the new game presumably has; however, I would prefer to have more complete individual arcs in single games than extended arcs in multiple games.

Besides, DA's method of bringing characters back as NPC works quite well. I think seeing their characters grow beyond our protagonist is actually more valuable than simply meeting up with them again.

Exactly as each game even in the ME trilogy has it's own arc which includes a beginning a middle and an end. ME1's was the fight mostly with Saren and stopping him from destroying humanity which was how Shepard got pulled into the reaper business.ME2 was about stopping the collectors from doing the same thing desrtoying humanity. ME3 is the reapers themselves now having a go. So eacxh game essentially is it's own individual story because you are fighting a different enemy in each of the 3 games and as such the series  can be played that way if the player wishes to. Yes you had the reapers going on throughout all 3 games but that was the overall story but they were still individual stories within that overall story

It depends on how carefully they write.  Closing off plot lines and tying them up could keep this problem to a managable number.  But its probably easier to just switch characters each game. 

They'd have to have the entire multi-game arc planned out. They'd have to know what effect the rachni being there or not would have, the state of the Council, etc, and account for it across several games. And they'd have to somehow introduce new companions while keeping the old ones, while not getting too bloated a companion list. And account for the presence or absence of all of them (not to mention. They'd have to be able to devote equal time to each and every LI they introduce. And account for players romancing them, staying loyal, cheating, etc. (not to mention demands to kill companions, which for some reason keeps coming up) And the Mass Effect Trilogy pretty well demonstrates they aren't willing to do that.

Instead we get "LOL let's close off the plot lines by killing the character off for a couple of years, then bring him/her back to life with 'resources'!"

I really liked having Shepard through three games and watching her relationships with the squaddies evolve over time. Having a new protagonist means new squaddies each game and I don't really want to do the "who are you and why are you joining and yes, I can help you with your daddy issues" every game. One game is long enough to get fairly attached to the characters, but not nearly the level of attachment I felt for the MET characters. I also don't really like carryover NPCs with new protagonists, like Oghren, Anders, Varric, Cullen, Leliana, etc. I don't want to get to know them again as a new PC, I want to continue an established relationship. They just add baggage otherwise. ("Hey, Alistair, I know I'm the Inquisitor and we've just met and all, but I really want you to tell me how much you love the Warden in great detail.")

So all in all, I'd rather have one protagonist and one squad for multiple games -- but only if I really like the protagonist. I loved Shepard and her crew and would gladly play more games with her (Post Destroy Oregon trail to Rannoch, anyone?). On the other hand, I loathed Hawke (no offense to Jo Wyatt, it wasn't her fault) and would not be interested in playing multiple games with her. The Inquisitor was fine and don't think finishing Solas' story with a new protagonist will have the same feeling of gravitas as finishing it as the Inquisitor (though I know that won't happen).