For a tournament where an ante is introduced in a later round...
Thoughts on pros and cons for a BBA vs just increasing the BB amount to equal BB + BBA?
This is a good question. It's mathematically a different dynamic, so depends on what you want to encourage. You're talking about dead money versus a live bet. For example, for antes at a 400/800 level, if you add a BBA for 800 (or traditional antes of 100 at an 8-handed table) that means the cost of an orbit is 2000 chips. With a no-ante structure, to have similar stack depth you would either be at 600/1200 (1800 chips per orbit) or 700/1400 (2100 chips per orbit). If you just add what the ante would be to the BB, you get a BB of 1600. I'm not sure if you're asking about having the SB remain at 400 (400/1600) or adjust the SB accordingly (800/1600).
With antes at this level (BBA or 8 traditional antes), a player can raise to as little as 1600 to take down the 2000 chips in the pot. That's a bet of only 80% of the chips one stands to win. And facing a min-raise, the BB is getting at least 4.5:1 to defend the BB depending on whether there are other calls. With no antes (using 700/1400 as an example, but the ratios are always the same), a player would have to raise to at least 2800 to take down the 2100 chips in the pot. So the bet is 133% of the chips to be won. And the BB now only gets 3.5:1 to defend the BB. There is mathematically more incentive both to raise and to call when there are antes in play.
If you are suggesting just adding the BBA portion to the big blind without adjusting the small blind, e.g., 400/1600, now a player has to raise to 3200 chips to win the 2000 chips in the pot. So the bet has to be 160% of the chips to be won. And the BB now only gets 3.25:1 to defend.
Of course, some players will raise and call with any of these options. And in a tournament there is always the upward pressure of the blinds to incentivize players to play hands. But the range of hands that thinking players
should be playing is wider with an ante structure, so it's up to you whether that's something that you want to encourage.