HAH. A PCMCIA 16-bit card would be akin to installing an ISA card. A PCCard 32-bit would be like a PCI card. But of course they wouldn't be anything like a full ISA or PCI card, due to the space constraints for the size of the video chip, memory, cooling, et cetera. You might get maybe Riva128 power out of one. 🙂
Dell has a few laptops I think that allow a video card upgrade, via a mini-AGP slot. Whatever you buy now has the video in such a slot, and you just buy a replacement. I think they may be the only one. You'd have to get the full specifications or manuals for any laptop you want to check.