Yes wouldn't you love to have a coin which you can change all of the parameters on the fly with no need to hard fork and get everyone to update?? Sounds amazing to me, so I have started some preliminary development on it. Unfortunately it is a very very busy time of the year for me, so can only do limited work right now.

Is it possible to add the option of locking per staking bracket? it could be maybe with a drop down list with options ranging from unlimited to the current brackets - 256 days, 128 days etc
and of course once it reaches the max locked days it will automatically unlock and be ready for staking.

what do you think?

could you be more specific, please

Summary

RateCoin (XRA) is designed for long term oriented minters. XRA uses Proof of Stake to secure its blockchain and is designed with long term sustainability as its primary focus. Stake rewards are generous enough to encourage holding and minting of the currency, but are low enough that inflation problems should not emerge. RateCoin gives incentive to long term holders to take coins away from exchanges and stake them long term, in theory this should create an upwards pressure on the exchange rate between XRA and BTC or other currencies.

XRA is also designed to scale long term. Small time intervals between blocks creates blockchain bloat and can lead to a nearly impossible chain to sync after a year or two of operation. Large blockchains take lots of resources such as disk space and memory. RateCoin is designed with a 3 minute block target, meaning that approximately 480 blocks are added to the chain per day, 175,200 per year. Compare this to coins that have a 30 second block time that add 2,880 blocks per day, 1,051,200 blocks per year. The problem is that when a node syncs it has to scan and store every block. It is fairly easy to download the blocks, for example getting them all in a bootstrap.dat file doesn't take too long, the problem is scanning all of the blocks which can take days for certain nodes if the chain is too large. A large chain can prevent an exchange from implementing the coin and can make users hesitant to run the coin. RateCoin is designed to avoid these problems and easily scale over a long period of time.

XRA's Reward System

High Rewards for Long Term Holders: XRA calculates stake rate based on the age of the input that is used in the stake transaction. The reward rate starts at 0.25% for any input that is less than one day old. If the input is over 1 day old the stake rate bumps up to 1%. For every doubling of days the stake rate moves up by 1.5 times (up to the top bracket of 25.6289% after 256 days).

Minimum rewards given to ensure the network remains competitive: If XRA only gave generous rewards to those that lock away their coins for long periods of time, the network difficulty would be very low and there would not be enough available outputs to stake to keep the blockchain moving. For this reason XRA gives a minimum reward of 100 XRA to any stake input no matter what the size. This means that if you are able to stake an input of 100 XRA, you will get a reward that doubles your input. On the other hand if your input is old and large enough it will well exceed the minimum reward and default to the normal age based rate brackets.