I have fairly significant search experience, 20+yrs with 11 years of professional experience including 7 EMS with secondary search duties and 4 years of experience when my primary duties are rural search and tracking. I've done a good bit of search/tracking at night. However, seach duties vary from area to area, so let me add a few thoughts about your lists. These are just my experience as to what works for me in the areas I have worked. YMMV.
1 primary flashlight (2c or larger)
A big flashlight has no place on my belt or in my pack. Why?
First, there are many small lights that are brighter than C or D cell lights for "bright light" uses. Bright lights are primarily used for tactical situations (basically blinding bad guys), not searches. If you are stopping through the wild waving a bright light around, your not focusing on the dirt as you should be. I do carry a tactical bright light, a rechargeable Streamlight Strion. Recharging is a must have feature because I end up using the light every night and 123 lithiums aren't cheap. A small spare Strion battery or two along with the light weigh about as much as two spare batteries for a C or D cell maglite. If rechargeability isn't important to you, you can buy low cost tac lights at Chinaworld for not much these days. A small light allows me to carry more water.
Second, my primary flashlight for search/mantracking is a 3AA LED streamlight task light. Contrary to conventional wisdom, night time is the best time to mantrack. An LED (especially when used at a low angle) throws excellent shadows and makes tracking (or cutting for sign) easy. In my experience, trying to use a bright light for night search operations is severely detrimental to your efforts. The bright light will often washout the footsign making it much, much harder if not impossible to track especially with the older windblown sign that you are often forced to try to follow in a SAR situation. The LED light will last for several nights of continuous use. And a few spare AA batteries will also serve as backup for my other items, GPS and nightvision. I wish I had the option of carrying a AA powered handheld radio to simplify my battery needs.
I personally will never use a camel back rig.
I carry a camelback with two 3 liter bladders, and it's barely enough for use in Arizona. I too am not enamored with bladder type packs. It's an ok idea, but I find that when I really want water, I have to struggle to suck it out. It works for sipping, but you cannot gulp down a large amount. Once you find the person you are searching for, they will almost always be in need of fluids. Camelbacks just don't work well for sharing. You can open the cap and pour it into something, if they have a cup. I often carry extra water in 1 liter bottles off the shelf (aquafina or whatever) and sometimes freeze one to keep everything else cool. But all in all I find that camelbacks are more hype than function. One could get by just as well with a Nalgenes or similar bottles.
I actually prefer the GI 2 quart canteen, although there is no canteen cup to fit on the bottom of it like the nalgene.
Also, add a taylor's cloth measuring tape or other small measuring tape to your kit. Measurements of the footsign are the first thing you need to communicate when you are tracking.
basic tools (srew driver, pliers)
I carry a pocket multitool. I prefer one with a serated edge, saw, can opener, and, of course, pliers. A few screwdriver options are there as well. Brand wouldn't matter much to me.
Not sure if you are thinking of tools for extrication or not, but I wouldn't issue each guy a set of these. The weight adds up quickly, even if you only add handtools and a prybar or hacksaw. I would carry fluids (canteens and maybe IV) before I carried handtools. The search team member will have to rely on another responding unit to bring extication tools, folding stretchers, O2 and all that stuff, if needed, once the quarry has been found.
As for the pack, all of those mentioned seemed good enough. I would try to keep the gear as light as possible. I've seen many excellent sar types who carry little more than a buttpack and canteens. I'd probably start there and add a small pack if necessary for the amount of time you will be in the field.
EMT's tend to pack more medical gear than they really need. You need to be light and cover plenty of ground with as little fatigue as possible. And you must carry water, maybe lots of water. If you're tired, you are more less to find the subject. Finding the person, then beginning to warm them and hydrate them while the cavalry responds is the goal. Carrying extra sam splints, pony 02 bottles, or extrication tools can weigh your searchers to the point of ineffectiveness. Don't forget the primary goal. You must avoid the temptation of getting too big a pack and doing just that.
As far as the lights go Skammer is correct that this is mainly an urban/ suburban environ, as im sure you know More light is often needed to search these areas because of shadows and glares from street lights, porch lights, passing cars etc. Plus my guys may find themselved directing traffic, or crossing streets, I want them to have a good amount of light, I am looking right now at the Brightstar 4 AA, And mabey a head lamp. ( I have the brightstar angle head and its Fantastic)
I would definitely suggest something EXTREMELY modular. Your not gonna want Masscas equipment on most searches. If the pack is left in the truck all the time, you're wasting your money.