I was looking through the new WD earlier and I started wondering if GW will do smaller starter sets for MESBG? I've not interest in painting large armies like Pelennor Fields but a couple of smaller skirmish forces might be fun.
You mean like the getting started boxes they have for their other games? The main limitation is that those sets only contain plastics, a playable army requires characters to lead it, and there are very few plastic character miniatures in the range (just a handful of named ones and some boxes have the option to build captains). Although there will be more plastic characters in the future apparently. Of course, a small starter for this game just means one or two boxes of troops really - a box of 24 warriors and one of 6 cavalry gives you a very playable force. One more box and you've got a fully fledged army in many cases.
If by skirmish you mean a dozen figures a side, the Battle Companies system may be of interest - it's SBG's version of Mordheim, using the standard rules and profiles for the game, with a campaign/experience system added on. Single sprue of most warrior types will get you a starting warband (with spares); add a single blister of each of the faction elites and you're set for a full campaign.