I don't really think "building" an NPC is necessarily the best idea. In a system which is thoroughly balanced like say DnD 4th edition it would make sense. Thank god SR4 is not a very balanced system and spending 400 BP on a character is really not a great gauge on how "hard" that character is when up against your PC's. Balance in a system is a recipe for homogenization or WoW'fication and any good story telling game is not gonna worry too much about "balance." As long as they're rolling dice for something and have a finite probability of success, then that's balance in my book. For this reason I feel it's best to just give your NPC's the stats, spells,cyberware, abilities, etc. that you want them to have. This saves you a whole bunch of time and makes things as balanced or unbalanced as you want to have it. I mean, look at the
min/maxed sample archtypes. They were built with 400BP just like the ones in SR4A...but they are LIGHTYEARS more powerful. So i feel it's very much an exercise in futility to try and gauge how "tough" your NPC's are based on the BP or even Karma systems. Just pull each one of their stats etc. out of your ass and just use the actual dice pools they're getting for the stuff they do as the gauge for their actual level and in terms of the dice pools your players are coming to the table with. This will make things far more balanced and is far less tedious then full blown character creation. I have seen GM's put so much care into "constructing" NPC's that just get blown away and all that careful construction just gets flushed down the toilet. It's too easy for that to happen in SR so make sure you're not putting too much energy into building NPC's. Take that time and energy and put into plots and storylines instead.
Just remember, if you're playing SR, chances are your NPC's will get pwned and if they don't get pwned then they will decimate your players. It's a very "see-saw" type of system....which is realistic. How often do you have drawn out gunfights where people slowly get wounded enough times to drop down dead? I found that the best way to try to hit that sweet spot in the middle is with their use of Edge. If they're getting pwned give them a lot of Edge and have them use it liberally. If they're too tough then back off on the Edge use. Another great way to balance is the use of cover and tactics. Power-game your NPC's just as much as the players are power-gaming but have it all depend on if you want the Players to succeed, or failure would be a cool plot twist or teach them a good lesson that keeps them motivated. The goal here is to make you're players feel like they're doing bad-ass stuff but they're working hard to survive. Give them the illuson that they're getting lucky.
If you really really want to stay close to "400BP" just take characters you've seen people make on PbP or NPC's from different adventure sourcebooks and then tweak them however you want without wasting time with calculating their BP's and then rearranging how it's spent and keeping track of BP. It's a lot of work with no payoff.
Note to players in my OWN games: I am building every single NPC from 0-400 BP and am trying to kill you at every turn. Pay no heed to what i just said above!
