1) Hard fork is by far the best option. A "restart" should only be the last resort if the hard fork is impossible, or itself fails (for example, has an error that kills the new chain, or too many people stay on the old software).
The canonical way to hard fork is you put the old protocol code in IF blocks, like this:
if (nHeight < NNN)
{old protocol code}
else
{new protocol code}
so the historic part of the chain accepts. Many of the altcoins have such scattered all over the place.
Also, remember to leave a long enough window that people can get the new software installed (several days at least). I know it seems urgent that faulty votes/credits may be getting in, but discrepancies of a few blocks/coins are minor relative to tossing the entire 30000+ coin history. Everyone on-board understood and accepted there might be some experimental snags.
2) In a restart scenario, it would be wise to maintain the original idea of preserving the balances (best effort), unless it's just too hard (eg. too many accounts to track by hand). Most/all your early adopters put in significant energy and time experimenting and shaking out the bugs with that expectation, and a poof scenario will demoralize their enthusiasm and support.
3) In the life of a coin, you get maybe one restart, and after that you're in "can't get fooled again" territory. And a zero restart, especially on a new port address, is effectively a new coin, with the added baggage of having already "failed" once, and discouraged early adopters. Especially for a cpu coin, that leaves you the botnetters - not exactly the most community-minded group. So IMO, we shouldn't even be voting on it, given that the much better options 1 and 2 above are still open.
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Other Notes:
* Reducing block maturation from 120 to 45 seems fine, though probably unnecessary.
* In regards switching ports on a restart, keep in mind they are a limited resource, and there is already growing contention among the altcoins. The community cannot really sustain each coin variant grabbing 1, let alone more. Is it necessary in the hard fork case? Other altcoins are hard-forking all the time, and I have never heard of a port change.
* 6 minute block time (mentioned above) is a *feature* for security and robustness, not a bug.