To make it clear, if i haven't already, the problem I have is the concept of creating roles where there is no need to aim even at a high level. I like the concept of adding more to a role then simply using a weapon, of applying moba like abilities for example, that demand more of individual players then simply using a gun well. A deployable could fit that quite easily.
I think there are a lot of weaknesses to the traditional ctf mode. Defending and doing nothing isn't fun and if you add deployables, the busy work of setting up deployables isn't what a traditional fps player would be consider fun. In pubs, where the majority of people are idiots it can be difficult to coordinate your team to both defend their flag and attack the enemy flag. Not to mention spectating being a near impossible feat if half a team is playing defensively and doing complex, unpredictable things, while at the same time the other half is playing offensively and doing complex, unpredictable things, and the other team is doing the same, thats at least 4 complex unpredictable things each involving multiple players, each happening at the same time, all very important to the outcome of the game, seems like it would be near impossible to spectate and follow.
I think a singular objective is ideal in that it is simple for strangers to all work together towards the single objective and it is easier to spectate and follow. In most traditional sports, there is a single objective, a ball of some kind. I think the objective moving is one of the things critical to the success of the ball. How the game changes if the ball is close to a goal helps create climaxes. The 3 singular, mobile objectives for fps i'm aware of is some modes of ctf, a ball which is like a flag, but you can pass and maybe shoot it, and i guess i could call it mobile capture points, like the push carts in tf2. I think the objective being greatly effected by netcode, like projectiles are, would be poor design, so i'm generally against a ball objective in fps. But i think either of the other two could work great. If designed with avoiding classic pitfalls like stalemates.