Nothing prevents you from ICO. There can be two main options, as I can see: a Kickstarter-like crowdfunding campaign just to collect money for your newer platform version and a full-fledged blockchain-based project with a token-depended ecosystem. The latter one seems more attractive for both your actual customers and the crypto fans who can become the new users of your upgraded platform. The general suggestion in this case is to ponder the functionality of your tokens to make them the only mandatory link between your platform and the users. In other words, represent your blockchain project ecosystem as the unbreakable “platform-tokens-users” chain. Creating your project whitepaper, do your best to convince your potential token buyers that blockchain is a highly recommended (and even compulsory) technology for your newer platform version. Good luck!