If you intend to increase the liquidity of your tokens as much as possible, then limiting the purchase to 2 Eth may not be the right way to go. If you do this, then you hinder the increase value of your token. I appreciate your concern of centralisation but this is something you will need to deeply consider.
My thoughts are the following: if all of the tokens have not been purchased (7.6 billion), consider burning the ones that have not been sold. This will increase the value of your token in line with the demand of your ICO and the supply of your coin. See example below:
- 7.6 billion coins are offered for purchase by the public
- ICO ends and 2 billion coins are purchased, price of your token is valued at £0.20
- Burn 5.6 billion coins that were unsold, value of your token will increase to £0.60 (price is an example).
Increasing the token supply to each individual, incentivises more participants to join the ICO round. Especially, if you give the individuals bonus for early participation.
As we discussed, we shall that a limit of 10 ETH per individual in the ICO round may be viable.