you could mash higher temperature and get more body, but it will give you more higher sugars that dont ferment so you will get more calorie in your beer. Alcohol gives more calorie than unfermentable sugars, so better mash higher temp.
you can also use some caramel malts or some wheat malt to get some protein. or just use a little carapils/carahell/dextrinmalt, i think it would help your experiment
Mashing higher will give the beer more residual sugar and thus better body, but more calories per unit alcohol.
OP can you post your current recipe?