Well deferred rendering is totally out of the question then.
1. It doesn't work on iOS
2. Transparent stuff falls back to forward rendering anyway, which is totally useless in your case.
There is another solution, but its still in development (it works), and it will be a cheap paid add on to 2D Toolkit for lighting.
http://unikronsoftware.com/2dtoolkit/forum/index.php/topic,783.0.htmlI will be looking for beta testers very soon now (its been in limbo for a while), perhaps you might be interested.
There will be no shadow support in that solution, and no support for normal maps in the initial release.
The normal lighting path isn't THAT bad. It may be 3 draw calls for 1 sprite, but it'll be the same number for all batched sprites which are affected by the same light. So 3 draw calls for 100 sprites using the same material, illuminated by the same number of lights, too. Depending on your needs you could further optimize this using vertex lights only to speed things up further.