all transactions are to be included in the blockchain..there cannot be any transaction outside..

off blockchain transaction simply means that a ledger is maintained outside the blockchain and then injected into the official blockchain after some time, typically what happens in coinbase and in some altcoin exchanges..

speed is one reason i believe reason for off blockchain tranaction.

See here. This is the place to establish your competence, not to obfuscate yourself and your idea while appealing to "ease".

How secure are we talking?  After the rash of hacks lately I am going to need a little more info.

Right now we have about 22 users.

Over a year ago I actually started importing the blockchain and doing just that, but it requires the full blockchain imported into MySQL or your preferred database.

Blockchain.info and others basically read the blocks and makes a database following the inputs/outputs.You need a block explorer for what you want.

Supply is fixed!

I think what OP is getting at is that there will be a perceived decrease in scarcity when there are more readily-available outlets for people to trade in Bitcoin. Now you sort of have to know someone who knows someone or know the secret handshake. The amount of work or knowledge necessary to obtain Bitcoin will in fact decrease. The cost to obtain Bitcoin (separate from its trading value) will go down.

A good analogy for why this doesn't match up with reality is this:

Imagine a store that sells only one thing. Lets say it is hot cocoa. This store is at the top of a big hill which is surrounded by trees and covered in snow. Everyone in the town near the hill is shivering and cold, because they have never heard of hot cocoa. One person climbs to the top of the hill, which is very difficult because the snow is deep and the hill is treacherously steep. That person gets to the top and the proprietor of the store has four steaming hot cups of cocoa, which the proprietor offers him at a dollar per cup.

The climber, however, has left his wallet at home. He fishes through his pockets and finds a dime. He says, "sorry, that's all I've got." The proprietor looks around, sees he has no other customers and is unlikely to sell any of his cocoa, and says, "what the heck, no one wants this stuff anyhow" and sells the cocoa for a dime.

The next day, the climber brings three friends, and they've all brought their wallets. It's a tough climb to the top but everyone gets to the cocoa store and spends a dollar on the hot cocoa. Everyone feels so much better after a lifetime deprived of hot cocoa that on the way down they start shoveling a trail through the snow to make it easier to get to the top of the hill.

The following day, there are eight people. The trail made climbing the hill much easier. They all get to the top, but there are only four new cups of cocoa. The first four people get their cocoa, and when it comes to the fifth, they ran out. So one person without cocoa offers one of the people with cocoa a dollar for half of their cup of cocoa. The first people in line dole out half their cocoa, make their dollar back, and think, awesome! I just got my cocoa for free!

A few months later, there is a road going to the top of the hill and regular bus service. Everyone wants cocoa and it's not hard to get to the store anymore. The proprietor is trying his best to make as much cocoa as he can but even hiring a couple of people to help he can't make more than a hundred cups of cocoa because the cocoa machine only makes one cup at a time. But four hundred people are visiting every day because everyone knows where the cocoa shop is and how much better it feels to shiver in your wintry fairytale existence with a belly full of cocoa, and no one has to work hard at it, just hop on the bus.

Um. Then the writer realized he'd spent a half hour of his life on a stupid fable about cocoa. A half hour he'll never get back.

The moral of the story is: some people, like me, ought not be allowed on the Internet.

The end.