The only limitations for what you can build are the capacities of the derailleurs involved. If you have 46-30t chaingrings in the front, and 11-42t x 10 speed cassette in the rear, you would need a derailleur system with 47 tooth capacity. My touring bike has a rear derailleur that can handle this, but 47 tooth capacity is the largest I have seen for sale. Of course, there will also be a limit to what size large cog a derailleur can handle, as going too big will cause interference with the derailleur pulley wheel.
For the front gears, you need to make sure the derailleur can reliably handle whatever jump is between the chainrings. Usually the manufacturer will tell you the limits, but I've never seen one that can reliably handle more than a 16t change. Here's a calculator where you can play with your planned setup:
Bicycle Gear Calculator
One more item: your low gear (30x42) would give you about 20 gear-inches, which is very useful for exceptionally steep climbs and/or climbing with a load.