Strobes/grip/modifiers:
My only caveat is that you may discover that what you want/need now, may be
completely different after experiencing a year's worth of more varied assignments. The Profoto B1s are awesome for on-location fashion with an assistant-held modifier, positioned relatively close to your subjects, but for larger set-ups, you may need a lot more than 1,000Ws of portable power for shooting daylight exteriors (e.g., 2,000-4,000Ws). In fact, for many exteriors, a lot of pros use extremely large scrims and reflectors in addition to (or, in place of) high-powered strobes.
My new favorite lighting-control system is Lastolite's re-designed line of portable 6.6' x 6.6' Skylite scrims and reflectors. However, for bigger set-ups, even larger scrims may be required (e.g., 10' x 10', 20' x 20'), plus the requisite pile of ultra-heavy grip gear to rig it. I would consider spending a fair amount of your budget on grip alone (steel location stands, booms, shotbags, scrims, reflectors, etc.). Then again, I've seen a ton of high-profile shoots photographed with just a stupid California Sunbounce reflector:
Personally, I took a piecemeal approach to building my strobe set-up. I basically built separate systems, designed for different types of shoots. Initially, I bought a pile of Speedlights, but the first strobe I bought was a used Dynalite Uni400 AC/DC monolight (which also included a Chimera QR speedring, 18" Dynalite beauty dish, and a Jackrabbit II, all for a fraction of what it would've cost new). However, in retrospect, I wished I would've purchased a pair of Elinchroms (for direct-mounting of their excellent "foldable" modifiers), or a couple of Einstein E640s instead (for their extremely wide power-range).
Later, I purchased a couple of open-box Speedotron Force 10 AC monolights (1,000Ws each), for high-output daylight exteriors, plus two, used Dynalite XP-1100 AC inverters to power them. Total damage: just over $2,000 for 2,000Ws of battery-powered, location strobe lighting (of course, Watt-for-Watt, this only cost a quarter of what B1s would've cost, but it weighs five times more!). Now, had I to do it all over again, I may have chosen differently (although, I'm very happy with the performance of the pair of Speedotron/XP-1100s I own), and of course, I'm still pondering what to do next (see
my post in another thread here). While almost anyone's modifiers can be mounted on any brand's strobes, there's certainly benefits to staying within one brand for both strobes and modifiers. FWIW, here's my brief take on the modifiers I've bought, or am now considering:
Profoto RFi:


• Canvas-like build
 (i.e., "durable," but
heavy).
• Silver interiors (my preference, since they're cooler than white interiors).

• Recessed-fronts accommodate Velcro-attached softgrids.

• Available softgrids for the entire RFi product line (but I've substituted less expensive, tighter grids from other manufacturers).

• Special features: None, other than their color-keyed speedrings.
The Profoto modifiers I've used and own are well-built, but their larger modifiers (e.g., 4' x 6") are simply too heavy for their rods, and permanently bend out of shape within a few hours (I had two 4' x 6' Profoto softboxes, which I promptly returned). I own a 3' and 5' Profoto RFi octa which I use with both Speedlights and monolights. Contrary to popular perception, their smaller RFi softboxes are fairly affordable, and in fact, their 5' octa costs less then Photoflex' version. One thing I do like about Profoto is their Dynalite speedring--one of the most secure designs available. But, their speedrings made for non-Profoto strobes are heavy, made of solid steel, adding even more weight (and, expense) to your package.


Photoflex:


• Nylon build (lightweight).

• Recessed-front.

• Available softgrids.

• Special features: Patented "Quick Release Corners."


Lightweight and decent quality, and most are reasonably priced. Their nylon construction makes them extremely light, which I like. I own a Photoflex 54" x 72" LiteDome which weighs almost nothing, but I also bought a similarly designed, nylon Calumet 54" x 72" softbox at their liquidation sale--I couldn't resist [note: it's better to buy all the same brand when purchasing white-interior softboxes]. For a softgrid, I bought the Calumet grid which was significantly less expensive than the Photoflex-branded grid.
Elinchrom Rotalux:


• Nylon build (lightweight).

• Flush-front (does
not accommodate softgrids).

• Special features: Unique "umbrella-like" design makes for rapid set-up/tear-down (possibly the most attractive feature of the entire system).
I haven't used these myself, but I think they're next on the list. I can't tell you how much I hate building traditional softboxes on-set,
including my Profoto RFis, which incorporate no such innovations, and plug into speedrings the same way every other softbox does. For any particular job, I usually build them at home and bring them on-set already pre-built. Sticking steel pins under tension into 8mm holes is not my idea of fun.
You seem pretty set on getting the B1s, and that's fine, if they fulfill a specific requirement that's appropriate for that particular tool. However, keep in mind, that your needs/tastes/working style may change as you take on more varied assignments, and may require acquiring a completely different set of tools in the future. Good luck!