Yes you can. You'll need to play each one until they have at least one companion. Ideally play until they get their ship so you have both companions available. It makes running missions and crafting much quicker. A word of warning: it can become a massive time and credit sink. I created an army of alts, partly to check out each class and partly to become self-sufficient. However, the amount of time and money you need to spend on mats, recipes, crafting missions and just switching between the alts is huge. And it's pretty much constant because you level so fast you are always outgrowing your gear and need to make more. It's been interesting trying out each class and all the different crew skills, but I've now switched my main to biochem and am going to play just that toon and use only commendations/loot/GTN to gear up as I level. So if you decide to go the crafter alt route I'd recommend restricting it to just one or two unless you have a LOT of times on your hands. Good luck