The issue you'll have is chain rub due to the more narrow cage of the 10 speed front derailler. You could compensate by using a 10 speed chain but you'd be adding needless expense. 9 speed would be slightly better in this regard but still not as good as 8 speed.
Why exactly are you replacing the Altus derailler anyway? While cheap, I've never had an issue with getting one to shift to my satisfaction.