Hehehe... here is my double-post. Hopefully Dozer won't smack me over the head with a newspaper! I have added new things... so read it all!

Before you design anything, go ahead and play with establish Squads in Campaign mode. Get a feel for the rules. I would suggest playing IG Cadian vs IG Cadian... it will give you the 'sense' of the little changes that make Death Squads so tactically different than other skirmishes. Make sure to play with the grenades... lots of fun!
NEW: This will also give you a sense of the items already on the game, which could serve you as a benchmark to design new ones. Many 'powerful' items appear to be toned-down... but instead they are still as powerful, with mathematical equivalents that still leave chance for survival. No auto-kills!
Give feedback on your experiences... good and bad. This way we will know if TLRB is well written or if we need to make revisions. Once you can call yourself a Death Squad vet, then we can talk about design. We have learned quite a bit in this project. One thing, is to design backwards. WTF?!? Hehehehe.... most people who design Warbands (for Mordheim) attack the problem by making units and stats first, then jamming the round peg on the square whole. We must design from fluff (form) to get to the stats (function.)
NEW: For example, you are already considering unit costs. For us, that is so low on the list is not even funny. WHAT?!? Yeap... the reason is NOT that is not important (it is critical!), but it happens that we (Dozer... I just watched) made a calculator. It gives an unbiased unit cost based on over 30 parameters. Sure you can eye-ball it; probably will get 90% of the costs right. But why spend HOURS eye-balling costs, when it can be done perfectly in 10 mins?
Unlike Mordheim (which has 15 warbands, 12 which are human), we have other races to think about. Ask Styrofoamking... just like you, he wanted to design a Rogue Trader Squad and we flipped him several times on his head. We are a tough crowd... MUHAHAHAH! Once we managed to convince him to get out of the box... OHHH BOY! The concept that he has for the Rogue Traders is... well, revolutionary. Simple, yet unique. Right now it is all on a diaper-stage (he has still a chance to mess it all up!), but he got us all giddy! I'm already looking for models.

Arrrgh!
Learn the game... help us with TLRB, Scenarios and so on. Once we know you understand the concepts and have met the Contributor requirements, we will be more than happy to help YOU make the Squad.
Now, to answer your questions/comments.1) I
'll read through the rules and have a look at the points/set up etc of the imperial guard you have the game.The IG Cadian are the game benchmark. Everything on the game (and I mean EVERYTHING) is balanced to be fair against them. No matter how crappy (Gretchins and Workers) or powerful (Space Marines) are the adversaries, all is balanced so it is fair for everyone. Do not concern about costs right now... we did all that for you already!

Concentrate in 'discovering' (from a design point of view) why certain rules are in place the way they are. We call it Ninja Design. It helps to know all those points, so you can design your own Squad around them.
2)
a points matrix for each item would be good to work with, so I could cost out weapons/equipment etc.We do have a calculator for unit costs, weapons and armor. We scratched what we had for wargear... and have to re-design something new. All calculators compare apples to apples, so it is fair over all. Wargear had proven difficult to put on the right matrix. You will notice that the Wargear costs are all loony. We will get it done... someday.
3)
is carapace armour used? Yes. It is part of the IG Depot.
4)
I know from reading some threads you are having issues with Space marine armour hence why the delay in the Space Marine scouts.Ahhh... the
Space Marine Conundrum. We are working the kinks via the Chaos Cultists. Their Leader is a Chaos Space Marine, and like all SM he presents a big challenge. While the specifics on this discussions are reserved for Contributors and Designers, in a nutshell part of the problem is as follows. The SM starts with 'super human' stats (read 4's and 5's), as well as awesome weapons (a Bolter is one of the most powerful non-specialty weapons) and Power Armor (potentially Save 3+) right from recruitment. On a traditional approach (designing like we did for Mordheim), this unit would cost over 250 credits. While this is fine (apples to apples) it present long term problems. The Squad size would have to be very small (5 guys) to make it competitive, but such a small number has a low Routing; the SM player could end up loosing lots of games. If anyone manages to kill a SM (I mean dead, not just OOA) then the SM player will loose a 250 credit model... he won't be able to recover in a campaign. It took 7 games for an IG Cadian player to recover from loosing 4 Officers in the 1st two games. So here we have a Squad composed of the most powerful units, that can't win a game. Not fun.
So we are tweaking and re-designing their recruitment and general behavior. The Space Marine Scout Squad (SMSS) will have one VERY cool SM (just like the Chaos Cultists (CC) have one), so we can prepare for the design of the Space Marine Chapter Squad (SMCS). We are taking our time... because they HAVE to be perfect. We are well in our way... it will just take time. Right now we (at Fort Myers) are the only ones play-testing things (and giving feedback), so we have been forced to stop designing new stuff until we test the current batches. If some group would test the Kroot...
5)
It won't be fast this investigation into the Adeptus Arbites as I do shift work and have two demanding kids. [Master2 and Miss4, plus she who must be obeyed] but I'll plod through and see what I can come up with.]
I understand... I have Da Boss and 3 mini-Mordheimers.

There is no hurry. We are here for the long haul... just play and have fun. Things will fall on their place.

PS--> Sorry... no Dreadnaughts... except a dancing one -->
