Now what I am going to propose can atcually be taken FOR ANY CODEX CHAPTER- Blood Angels and Dark Angels namely. You will see why the Wolves and Templars wouldn't really benefit from it as I explain.
So, as we know army variants are now driven by characters, and while in the past I have suggested that different doctrine-like qualities be applied to SM Tactics to get different Chapters, I have also come to realize that the standard codex really only supports Battle Company engagements.
That is that, unless you take a named character, you are typically limmited to playing 2-5th companies. While DA can also play DW/RW (which taking the named Character make sense for) and Blood Angels can claim to play as 8th Company taking assault marines as troops, the core for a SM army is TACTICAL SQUADS (meaning technically the reserve companies, 6 and 7, are "playable").
However, this is not neccesarily how forces are always deployed and battles always fought. So while I'd like to see my idea linked above put into place, I think the following would be nice as well.
1- SM Captains should have the largest selection of Wargear. These guys should have virtually EVERYTHING avaliable to the other than the specialised equipment of Characters/Chaplains/Librarians/Techpriest/Apothecary. Everything else should be free game. EVERYTHING. I think even heavy weapons, because if I was 9th Company Captain, heck, I'd possibly want a Lascannon. This way, there can be combinations and options just not available or affordable on other characters.
2- You should have the option to select what company he is, and with that, your force composition can change. This is where the SW and BT don't fit into the concept. Each SW Grand Company is pretty much a self sufficient force, with their own Blood Claws, Grey Hunters, and Long Fangs. Different Wolf Lords would have their own force compositions, and this match in fluff to force composition is already allowed under the current codex. BT are pretty much the same way with their Marshalls and Crusade Fleets. BUT Vanilla SM, DA and BA all have a structured orginization to their Chapter's companies. As such, wouldn't it be nice to be able to say "I want to play Ultramarines 9th Company" and be able to do it. Just massed SM firepower and siege capability, with a Captain geared for such a fight in stats, equipment, and rules? Maybe 10th Company. Sure you can fill your troops with Scouts as it is, but wouldn't it be even better if you could have a Captain in Carapace Armour leading them and rules to enhance a force of scouts beyond what their standard rules apply? What about 1st company? How come only DA have that capability especially when you read about it all the time- Battle of McCragge, Battle for Nocturne, aboard Space Hulks, etc. etc. An army of Sternguard/Vanguard/Terminators/Dreadnoughts ONLY. At the same time, certain restrictions would have to apply to each variant (EG- No Dreadnoughts in 10th company, no Assault squads in 9th). Obviously, the standard run of the mill captain would have access to the whole range of Codex choices, BUT not provide the benefits that a specialised captain would.
Now I think this just MAKES SENSE and would be FUN. Everyone like rules that match the fluff, and the point of the game is to be FUN contrary to what you may think (because winning is fun, but fun can be more than winning). It also would be good for the hobby aspect of the game, allowing for more unique forces, conversions, and characters.