If you have several hurdles before even the election day starts, you will get lower participation. A system excludes because: Some missed the deadline to register to vote, others feel it is too much work, and some are only confused by the process.
In sweden we have probably never have been required to preregister before an election or referendum takes place. (at least since World War1)
It is simple to use a registry from one (or combine from two) of governmental authorities.
In sweden there is used the official records from Tax-authority, because all people are registered there, if you are legal resident of the country, and are eligible for voting. It is not such an extra hassle for them, since almost 100% of adults have income and pay taxes, or they are receiving old-age-pension, unemployment checks or welfare. People with swedish citizenship, living and working abroad or in prison is also registered there.
So they can all vote by post. yes, even prisoners have democratic rights here!
(I.R.S.) (probably other federal governments have also good registers with all of the inhabitants that are allowed to vote) (Also there could be using all the Internet Banks login for a secure validation of all citizens in an online voting system. Banks have the combination of our identity, our account numbers and the login-pads)
I guess a simple system, that only require the voters to be active one time, on one occasion on one day, you remove important obstacles that can cause a lot of couchpotatoes from abstaining from their democratic right & Obligation!
Make the process so easy that noone can claim it was too difficult!