A friend and I were recently chatting about that idea. Blockchain voting (voting on ideas and issues in the conversation we were having, rather than representatives). The rough model we ended up at is that voting on most issues or ideas should not be compulsory but be a privilege earned through proof of knowledge and experience within fields pertaining to the given idea or issue. Due to the very nature of said model, it would probably extend out of some kind of blockchain system of transparent public domain and openly peer reviewed and debated tertiary online education knowledgebases so that people could choose to actively learn about relevant aspects of voting topics easily.

For raising new ideas or issues, it would also probably be linked to a wikibase of some kind which transparently holds the blockchain information regarding what happened to similar ideas and issues in the past, and an AI of some kind would assist to filter new ideas from ideas which have already been addressed or concluded, and ideas which draw legitimate reason to re-address old ideas.

Our conclusion has been said a bunch of times in comments here already: due to the level of potential for this system of democratic voting to be integrated into the rest of the blockchains likely to be around in the future (education, finance, medical, immigration, social services, etc); to do the job properly will require considerable time, planning, massive data communications and power infrastructure upgrades, and it will likely be heavily reliant on complex AI for the purpose of collating and sorting information. We'll be waiting quite a while for it to get to its full potential but if we're persistent and we start small by designing models which address local election levels (which various countries currently are) then it's simply a matter of time before it expands and becomes fruitful and truly democratic. The trick will be to push past digital voting for candidates and strive on towards a small scale system which works for ideas and issues in the face of massive opposition from those who stand to loose power, influence, and wealth.