I don't bond much. With an Ethereal on the table, it's fairly rare that your Fire Warriors will break and run, so bonding them isn't that useful. If I bond anything, it's large squads of suits. Your Stealth Suits should probably be bonded, so that they can regroup even if there's only two left. Any two or three man Crisis teams are also worth it to bond. Possibly Pathfinders, but I haven't play-tested it.
Railrifles are okay, because they add to the firing on the unit you're trying to erase, but I think that they're largely not worth the points. The only place they really shine is aganst Marines and Necrons because it's one of only three AP 3 weapons in the Tau armory. The other two are the Seeker missile and the Ion Cannon. It's up to you whether or not you want to include them, but I only have two, and they've never done that much for me.
Against Imp Guard, I would reccommend the Railgun. The Ionhead is useful, but the railgun submunition is LETHAL against Guardsmen. The secondary weapon is more of a stylistic choice than anything else. If you tend to run your tanks close and in LOS of units, then go with the two Burst Cannon, otherwise the longer range and no LOS requirements on the SMS make it more worthwhile. All tanks NEED the following upgrades: Multitracker, Decoy Launchers and Target Lock. With the MT on there, you should be moving over 6" every turn so that you can only be glanced. Any Immobilized results he gets on your tanks you force him to re-roll so you don't crash with the DL. The Target Lock will let you fire some nice S5 AP5 shots into his Guardsmen while still letting you take a potshot at his tank over there. The Devilfish really only NEEDS decoy launchers, but a multi tracker and a targeting array help alot.
The Crisis loadouts are more of a personal choice, because they're loadout depends on what role you plan on making them play in your army. As tank hunters, I find that a Missile/Twin linked Fusion is best for me, as I tend to get into trouble when I deep strike, so with this I can sling shots with the Missile Pod as I move up the field and have the twin linked fusion when it counts. The most popular generalist loadout is the Fireknife, Missile/Plasma/Multi. It does everything, but it's a little expensive and it's not best at anything. And especially with regular suits BS, these always don't hit when they're needed. Personally, I always run a Shas'o if the mission rules allow it. Having BS 5 is such a change, and all your shots should hit. The 4 wounds and bump up in the WS department don't hurt either. IC status means he can dance around in the rear and never be targeted, and Skilled Rider and Move through Terrain almost guarantee he should move far on his Difficult terrain checks and take no wounds from jumping into Difficult terrain if nesscesary. I suggest a shield generator if you're going to use either of the commanders though, it's no fun to lose an effective 3 or 4 wound model to an errant lascannon shot with no save possible.