Right, going out would entail a risk that you have fewer people at the last point, but it would at least be an option with a potential payoff. Part of the problem is that options are limited, and even with turtling, there are still a lot of moments where the defenders go "Wait, what, How'd they cap? When did the flag carrier get in here?"
Atleast if the map maker was able to balance the map with this in mind, it may work. But this, unfortunately, hasn't happened yet, atleast with the simple counter-attacks occuring so far. But i can see that recapturing the first protects the second again. My experience so far is of only a couple of the maps in the competition, but pretty much every second CP capture was a "wtf" moment. Interestingly people seem to have an affinity with placing their cp's in huts, presumably with the presumption that it means more protection and defensive capabilities for defenders when it just means a slower reaction time and time in general to deal damage to the courrier before he reaches the CP.
The tactics employed should be quite different ingame between A/D CP and CTF, but map makers are taking it simply as A/D being something that has a standard gameplay regardless of the mode utilised. Although they realise that the insta-cap is a problem (and the blocking capability has helped) i've seen no physcal regard for this fact.
Players need to settle somewhat into the new mode to get used to it and this will only happen through experience (of which there is little other than right here right now). Map makers also need to realise the pro's and con's involved for A/D CTF in order to design a map that doesn't fall into the basic flaws for which Valve dropped the mode in the first place.
For the general design of the maps so far i have noticed a fair assumption that players will be throwing themselves at a meat wall, but with the lack of instant respawn from TFC in TF2 this and a lot of other things are not the same. Thus the differing gameplay.
Maybe i'm just stating the obvious but it doesn't seem to be something that has been practicly applied yet, otherwise we wouldn't have a half-broken game mode still.
Valve did drop this mode for a reason and it will be difficult for people to pull out a response that works as well as Valve's CP replacement. Especially with so many of the entrants being inexperienced level designers.
But back to your point, how do you suppose a CP be retaken? I can imagine it being retaken like the standard CP would, because they lack their own intel for a start. but this would probably have to add time to the clock, it would be a dynamic that needs testing, but we're in the middle of a competition. As long as the flag remained stable between CP captures, the game remained balanced, that the counter attacks don't break flow and capture points could be captures by 2 different means, one by each team. I could see it as an
option.
I would like to see a more physical response to this design problem first, personally.