One small thing squire does for siege is measuring help. Range of Siege's gun is the same as the squire enchanced control area, which you can measure all the time.
Neroku check which Siege's abilities are dependant on the control area, you will notice that the small trash can helps with a lot. Also Siege is constantly out of focus as he likes to cast some of his spells like mage sight and fox hole, likes to shoot his gun and then give some to jacks. Every extra point counts in the second and third turns.
In my opinion every Siege list should start with Reinholdt, Squire and Defender. Those three models form a base for a solid list.
Some nice models on the article Malf