Can tankless & conventional water heaters join forces?
I see a couple problems there.  

First, having a tanked heater operate at less than 140°F (60°C) is problematic.  The reason is our science has advanced on the Legionella bacteria which causes Legionnaires Disease, and it turns out a "warm" water heater is a breeding ground for it and other bacteria.  140°F (60°C) is scalding, and that necessitates the modern style of mixing valve that automatically mixes hot and cold (It will not allow stream output to be near 140°F (60°C)). 

Second, using a tanked heater to "ease the load on" a tankless isn't much use, because the tankless doesn't need the help. It means the tankless will be barely working for the first 30-ish gallons (110 L-ish) of draw, the tanked heater is now useless and can't help.  The tankless will be working very hard.  If you did manage to overload this big tankless, everyone would go painfully tepid at once. 

The reverse connection makes more sense.  The tankless uses its full strength to warm the entering-the-tank water. Even at too much flow for the tankless, it's still giving a 40-60 °F (22–33 °C) boost.  Which dramatically improves the tanked heater's recovery time.   At flow rates the tankless can keep up with, you never run out of hot (at least warm) water.  At rates too much for the tankless, the tanked heater's recovery time (to a showerable 110°F (43°C)) drops from 30 minutes to 5. 

However, I am honestly not a fan of either one.  I don't like the tanked heater existing, due to its considerable parasitic load.  I would just go all-in on the tankless, and school people in "don't run everything at once".