IMO you can win with any defense as long as you have the right players. you're going to have to make some choices and some small sacrifices any time you rebuild a team but it's one of the more fun ways of playing the game i think.
as some have mentioned, pick your DEF and OFF now and stick to it. commit to it and don't look back for at least 6 seasons. as soon as you change your mind, you're killing at least 50% of any progress you have made already - perhaps more. i agree with isack, if you know you're going to play M2M and you're starting to recruit the players you think will run that well for you now, then switch your practice to it now. every minute the new recruits waste on a DEF they won't play is, well, wasted. i typically wait until i get everyone at a "C" or so before switching to playing it but you can switch to playing it now as well as you gain small improvements from game play as well as practicing (at least i think they made this change a long time ago).
if you don't mind playing zone, go for it. many titles have been won with zone and can be. there's no magic bullet defense. zone is just like any other defense in that you will need to make sure that where you sacrifice some ratings, you make sure you're fantastic in others.
for what it's worth, you've recognized a larger problem with your team and that is your just mediocre in ATH/SPE, which are arguably 2 of the top 4 ratings. whatever defense you play, you're going to need to fix that problem either way if you really want to compete year over year.
this is completely just an opinion but i would rank the ratings importance of each defense like this for me:
PRESS: ath, def, spe
M2M: def, spe, ath
ZONE: spe, ath, reb, def (you can make a case that you pick either ATH or SPE then put REB #2, then the remaining ATH/SPE third)
one final note, with proper patience and budgeting you should be able to attract at least 1-2 elite/near elite players to your program each season no matter what your prestige is. if you have 4-5 open schollies, you can potentially get between 3-4 of the elites...
they are out there, you just have to wait until they're a bit more ready to talk to you and avoid battles. you may already be employing this strategy but i use all the money for schollies to fill my open spots, minus 1-2 spots. essentially use your cash to go after 2-3 elite players and have 1-2 walk ons versus getting 4-5 good players. any penalty perceived or otherwise from carrying 1-2 walkons is worth using your cash to go after the best players you can get to. your previous season when you signed 7 players, if it was me, i would have signed 5, maybe 6 tops, and used the money from the 7th spot to use FSS more, do more evals, etc.