i would prefer NOT to see the spvp implemented, period, for all the reasons i've already made ad nauseum. let them experiment on federated servers.
i'm not even sure how you'd bring an altcoin into a SC with spvp since the monetary properties of such altcoins are usually so divergent and non-sensical to most Bitcoiners it wouldn't be worth anyone's time or effort.
If Side Chains run adequately on say LTC for long enough to see some of the tail risks play out, and we figure out how to handle those, then I would see that as a beneficial outcome.
On the other hand, some of the pernicious effects may take a very long time to work out, but we'd see them on LTC well before we'd see them on BTC. (Or even better some new coin designed with this as its purpose.)
That's the problem with tail risks. How do you know what is a "long enough time?"
This is why the catastrophic failure issue suggests there shouldn't really be one coin after all, and trying to maximize "network effect" may be over-fitting. Monoculture is fragile.