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This. As I have said before I believe in the open-forum discussing tactics and techniques but in light of recent attacks, terrorists have now established that bombing is not as effective as the Mumbai model of short-duration, multiple attacks by guns and homemade explosives forcing us into a position of having to take multiple shooter locations, some of which will be hastily established and defended by terrorists. I will gladly talk in PM with you but in all, all, I am happy for offensive tactics to be discussed so we can focus on destroying terrorist scum. You are right in what you say bria, and there are many ways to disturb an entry. I can say that no matter the casualties sustained, counter-terrorism teams will continue to go against the enemy, even at personal loss, and will continue to put the fight in their face, always. A well-positioned, well-barricaded enemy is near-always a hard target to defeat. This has been shown throughout history in many ways - think of machinegun nests, mine layers, etc. You are hitting the principles needed to defend a room effectively, at least against conventional through-door assault.
Bria keep your post. I am definitely not against you asking the questions, I am just on edge about answering currently. In reality, terrorists probably already know all of this and have thought it through. I mean some of AQ were ex-SF (Egyptian SF for example) who were trained by Western SF - including Delta. They know their shit. So it might be a fallacy, we're 100% welcome to your questions and you seem to already know it.
That said, it is in the fixed-state of airsoft. No explosives allowed. So the options become limited. Let me exemplify my thoughts on that fixed-state:
1. Limit routes of advance,
2. Prepare a weapon on potential avenues of approach,
3. Prepare to engage almost instantaneously and adjust for delay in entry,
4. Prepare secondary measures for follow-up such as grenades and further entry,
5. Even if the above is prepared. The entry team may use a multitude of TTPs to still blow your skull apart. Counter-terrorism teams ARE prepared for the above even if they face initial fatalities.
There are many resources on defenses in urban terrain. Including Fallujah and Israeli-Palestine conflict lessons learnt. Oil spills on the ground so people slipped. Anchor points from stairs taken apart of they fell. Explosive boobytraps looking like household objects. Offensive measures to counter this like turtling, lower-story demolition, stand-off attacks. The problems are when you barricade a house is that you're now the trapped mouse. Hence why no matter the defense, terrorist forces will all eventually die in place. Even if we have to wait them out. So defensive forces are not stronger than the attacking team, they may just have an initial advantage in some scenarios. The first volley of shots to get off, for example. Choke points can be opened up. A room is yours to expand when you have explosives or a sledgie. Stairs do not have to be negotiated when you have elevation systems and ladders. We think of one thing and find a way to defeat it. Tacticians will always find a way.
As I said, I am completely lost when it comes to specifics: how to create effective fields of fire inside, how to position inside rooms etc. 
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