I'm not sure why this would be necessary for storage purposes - at 10%ABV, there shouldn't be any issues with long term cellaring of this. I think it would be more trouble than it's worth to try to blend for higher ABV.
Brewers yeast will have a slightly higher alcohol tolerance if you want to end up with something less sweet in the 12% range. Many strains top out at around 12-12.5%. For something with a little more acid tolerance, wine yeast would also work well. I've used D47 in a JAOM, and it finished nice and clean without being quite so cloying as with bread yeast.