Transistors in parallel
This is actually a very common technique to do, both with BJTs (traditional transistors like drawn above) and MOSFETs. With BJTs, you don't need to bother with separate trimmed base resistors, all you need to do is add current sharing resistors or sometimes called ballast resistors. Look at this page for instance, the first one I found with google that explained this design: 

http://www.allaboutcircuits.com/vol_3/chpt_4/16.html

If you use MOSFETs, you don't need the current sharing resistors at all, they can just be parallelled 'out of the box'. MOSFETs have negative feedback 'built in': if one MOSFETs gets a larger share of the current, it gets hotter which in turn increases its resistance and reduces the amount of current going through it. This is why MOSFETs are usually preferred for applications where multiple transistors in parallel are required. However, BJTs are easier to built into current sources as they have fairly constant current gain.