Congrats bro, awesome car! You can't compare it with any other car in the market. Even the pervious Civic looks humble in front of the new one.
I don't think CNG would be an issue, many guys have installed CNG in iVTEC Accord. But if you're concerned about the hood space for CNG kit, leave it to them, hope they'll find some place to fix it.
If some one is afraid of fuel economy, please remember that it's an iVTEC, not a VTEC. It's far better in fuel consumption.
And to compare Altis with Civic...NO! you cannot compare
130hp 1.8 DOHC VVTi with 140hp 1.8 SOCH iVTEC
As a whole, VVTi just makes some humble 20% part of iVTEC. And what good is a DOHC if it's producing lesser horses? As fas as I see: there are a hundred thousand reasons to buy Civic, but not a couple of them to buy Altis.