What army? Well, what the hell have you been doing for 10 years?
- Aveline is captain of the guard, and in fact if you do all her personal quests, her guards are quite loyal
- Hawke is a noble, perhaps quite rich, and there are the Red Irons/or the Smugglers, depending on who he worked with
- Cullen, despite being a huge douche, is already questioning Meredith's orders, so there would be more than few templar deserters to join, especially if your brother is one of them
- The same on the other side of the coin, there are mages who refuse to use blood magic or go all nutso who would join you, especially if Bethany is one of them.
- There are a number of people you have helped, noble and ignoble alike, and things like chaos are bad for business, so the Coterie might be up for giving you a little aid.
- Any help from the Dalish might be iffy, and completely unlikely, especially if you slaughtered all of them.
This MIGHT have redeemed all the little idiotic things you did through out the game. If the Viscount's old secretary could be tapped to help organize the civic infrastructure for you, the ending would have been much more satisfying.