NON SPOILER SUMMARY: Awesome! Play the damn thing!
Cool mission, it was very inventive and I liked being offered a choice. I'm going to have to go back and select the other option! There wasn't much choice in dialogue but having that central to it, and early on, was great.
I love the "mobile turrets", interesting idea. The big explosion before you take over the Avenger is awesome too, but perhaps you might want to change the transition text - seems a little late on to be saying that. Taking a direct part in the past was great, the idea of being your own ancestor (almost a little warped, if you'll excuse the pun).
There were a few SPG issues around, especially in the history section (I've noted a handful below) and I don't like the assumption throughout that my character is a straight human male. Human might be necessary for the second part but altering the wording slightly would negate the other two.
A few small final things: please bring the gate just a little closer! Without full impulse, it is a bit of a dull start waiting to arrive at it. Also, without sensors I didn't realise I was aiming for the right hand side. I was going back and forth in front of it. Second, when you're on the starbase you didn't put any other NPCs. That's a great point to include lots of enemy aliens in Starfleet uniforms! Third, and this is just personal opinion the sacrifice of the Ent-C, not just its act of defending, was crucial to the alliance. By having the Ent-C survive it should be a weaker alliance, not stronger. Finally, I've been a bit of a moan-a-lot about Cryptic's new ship's name which you've used here. Avenger is not an appropriate Starfleet name, it is for any other faction or the mirror universe. There is a reason why it has only once appeared in Star Trek and that is as a mirror universe ship.
A few notes on SPG (I didn't get them all);
This is Vice Admiral [ FirstName]
Some of the text around Ent-C seemed like it needed work on grammar
"abolishing the natural zone"
"the federation vessel [ new paragraph ] USS Enterprise"
Jun-Luc Picard / an Energy weapon
Lots of lower case fs on federation throughtout
Secedes, not suseeds (Klingon names also mis-spelt in this paragraph and you're missing a full stop after fleets (flees).
"shortly after, the federation, the Federation the Romulans join the federation"