I have had the TopTier for a while, and have been running a HERMS system (hence the other two quick disconnects you see on the HLT). For that I was using two pumps at various points on brew day. I did drill a hole in the kettle with a step drill for the temp probe, as I did for the herms coil. Those are the only three holes I've ever drilled thru steel of any kind, so I can tell you with beginner's confidence that it was not hard, and none leak. I drilled it because there is a plug to close it easily, it wasn't hard after my experience with the HERMS, and I have the thermometer as a backup in case something isn't working.
Pumps: At the moment with a RIMS setup, I will just alternate or have a spare pump in case of a mishap on brew day with the two pumps. One I got pretty cheap anyway. Everything is wired into the controller switches you see on the front of the tower main pole, so I didn't want to do any rewiring to remove the one pump. There are other uses - ie. recirculate the HLT, or if my mash is too dark or caramelized in any way with the RIMS, I can use the second pump to go back to HERMS (eHERMS this time). Lastly, I may go back to a level HLT & MT and/or move the BK off the stand completely, so for now the pump will just stay put. (I'm a bit indecisive and/or ADHD about the best method/mechanism for how this works, but have gotten better consistency and higher efficiency throughout my changes).
My advise from my many attempts, rearrangements, etc:.... hmmm.... the Therminator reduced a lot of time and energy for sure, the TOP works like a dream (with water so far), the switch I wired onto the front makes it so easy to turn one flow on or off - it's not too hard or expensive - definitely suggest it, get some Home Depot gas lines a little longer than the Blichmann (makes rearranging your system MUCH easier), get a second pump as a backup or to pump wort from BK thru chiller and you'll have much less hassle with re-routing tubes (you don't need a third as I have, but get a second). Finally.... take the time to think it out before you assemble (I still may have to take this all apart just to rotate the kettles due to the wheels! I have the optional mounting bracket for the TOP before it was actually released, and not sure I want to mount it on the leg it is close to in the picture).
thanks