Yes, you can, but there are other alternatives to eliminating the plastic skirt.
If all you need is a skirting, and not perimeter support, you can build a wood frame and attach cement board (facing it with brick or stone veneer, for example) to give it a nice look. I know you can also get panels that look like a poured cement wall, but they're sheet-stock, like the cement board. Hardiboard is another choice as is NovaBrik.
I would go ahead and pour a footer, just to have the option of stacking something heavy on it later, even if I chose not to do it right away. It will make it easier to install whatever you choose right now (by providing a level surface to work from).
Depending on where you live, you may want to pour to below the frost line, and go ahead and add the re-bar. I would pour it so that it is at least ground level, especially since you mention raising the grade later, you may want to go ahead and pour it so that it will be closer to the desired grade level.
Most manufacturers require perimeter support at any entry door, or opening over 4 ft (sliding doors for example) - most dealerships, in my experience, don't bother to install them, because it would mean pouring more concrete. If a manufacturer wants to get picky, they can void the warranty for an improper set up. Therefore, while I was at pouring a footer, I would go ahead and install the support stacks near the entry doors, as required by the manufacturer. If you have the owner's manual to your home, it should tell you how the manufacturer requires your model of home to be set up.
I've seen a lot of alternatives over the years to vinyl perimeter skirting, including the plastic stone, stone/brick veneer, dry stacked blocks (low to the ground, only a couple of rows), dry stacked with stucco, cement board, Hardiboard, wood... all kinds of things. Think about what you want to do now, and what you want to do later. Its better to plan ahead, and prepare now, for what you want later, than to have to come back later, and rip everything out because you have to start over.
Don't forget to leave easy access to the underside of the home, hehehe. You don't want to have to crawl from one end of the home to the other, to repair a leak. Also, don't forget about cross ventilation - another requirement of the manufacturer, you NEED the ventilation under the home to keep the moisture level down. By the way - this is an excellent time to install a vapor barrier, if you don't already have one.