Planning for the End of an Arc

Over the weekend I posted a question to the Lead Developer's forum regarding some of the concerns I expressed yesterday.  Given that forum only has about an 80% reply rate, though, I'm not holding my breath for an answer.

In the meanwhile, I'm turning my attention back toward setting up session 14, which is the conclusion of both the Branth Bioweapons plotline and Clark's personal character arc.  This mission will be the first real base assault since the TerraSec building, so I'm approaching it much the same way: construct a layout appropriate for the kind of facility my players will be invading, then tinker with it to achieve the best dramatic situations.  In this case, we're looking as a super-secret underground bioweapons lab eastern Montana.  Unlike the TerraSec infiltration, I can give the party an attack plan via the Resistance for how they're expected to tackle this.

Given this an arc-closer mission, I want the stakes to feel much higher, and I want there to be a lot of excitement.  Fortunately, the abbreviated nature of Session 13 meant we have most of our session-start paperwork out of the way already; if I send the party the battleplan in advance, they can be ready to rock the moment we're done with breakfast.

So right now I'm brainstorming exciting events that will make this a memorable episode.  I'm thinking of making the initial complication disarming the base's nuclear self-destruct (ala The Andromeda Strain), which allows the Resistance to start capturing useful data and equipment.  Once the self-destruct has failed, a WarShip on orbit is reallocated to bombard the facility, but it needs to pass over the site.  Adjusting its orbit will take some plot-appropriate amount of time.  In the meantime, the party takes/destroys some critical objective, which they complete just as the bombardment starts.  The first few shells take the roof off the Branth enclosure, and some subset of the party escape using the Branths as mounts to escape before the next round of fire from the WarShip lands and destroys the remainder of the base.

It sounds suitably epic on paper, but now I need to plot out how I'm going to make this plan fly.