What are the viewpoint and lexical aspects of the following two stand?
You stand to make a lot from this deal.
They stand accused of crimes against humanity.
Would it be possible to use the present progressive tense here instead?
The stands in both sentences are stative:† they describe, respectively, the economic and legal status of the subjects. States are inherently imperfective.
As you know, stative verbs are not usually cast in the progressive construction, because they already have the imperfective sense which that construction bestows. When they are cast in the progressive, there is usually a sense that the state is at least potentially temporary; for instance, “You're standing in my way” is usually said to induce someone to get out of your way. “You’re standing to make a lot from this deal” is possible—you might use it, for instance, if you were trying to induce someone to moderate his terms, or to pass some his profit on to you! But stand accused is a fixed quasi-legal form; it would not be cast in the progressive, though standing accused of ... might appear as an attributive participle phrase.
† In fact, stand, state, stative and status are etymologically related. State is an Anglicization of Latin status, which is the past participle of the Latin verb sto, stāre, meaning “stand”: your status (or state) is, metaphorically, your ‘standing’—where or how you “stand”. Stative is a derived adjective. And Latin stāre is cognate with Germanic/English stand: both are derived from a Proto-Indo-European root sta-.