Looking at your question it seems to me that cycle time is more of an issue with selective solder than the .8 mm distance from the SOT. Have you looked at Stamp selective soldering? With this type of machine your cycle time is very fast and the hole fill is always even. As I see it, the only way to get your cycle time with selective wave soldering or point to point robotic systems is to buy multiple machines. On one you may have problems with the .8 mm distance to SMD and on the other you may have problems with uneven hole fill. Stamp soldering could be your solution. You will easily meet your cycle time requirements, the hole fill will be even all the time, and being .8 mm from SMD is not a problem.

Iron tip soldering robots are great for thermally challenged solder joints since you will have the ability to program each solder point with a different profile. While the heat (temperature) will have to remain a constant, you can program the amount of time the tip pr heats each joint and on some systems you may also pre tin the tip through a sub routine before applying solder. Post reflow times are also programmed to assure proper flow around the joint. Class 3 is obtained by programming the desired amount of solder to be applied. Most systems have very good solder feeders that offer a high degree of repeatability.

A variety of tips are available with some as small as 3 mm however most common is 4 & 5 mm. I also suggest that samples be sent to an OEM for soldering prior to making a decision. This would generally provide you with estimated cycle times, can the actual joint location be soldered? (or is the process restricted), and some generally soldering parameters, (heat, solder type, tip used, etc.).

The main problem I see is through put.

Since soldering robots are a point to point system, achieving high volume (per hour) can be a challenge. There are a few ways (product specific) to increase through put. Here are some considerations:

1) If you are running a multi up panel of smaller products, and if they can be arranged in a symmetrical matrix that would allow for dual irons to be used at the same time (basically solder two products at the same time) this will help with cycle time.
2) Multiple systems with side shuttles (two solder systems back to back). In a single line you can split the selective soldering process into 2 sub line with the shuttles. This allows for products to be separated for independent soldering and then combined again before next process delivery. Also, with selector switch capability you could turn on and off the flow to allow for servicing of one system while continuing production on the other.
3) Buy multiple machines.