Interesting situation… There is a nice (not great) book on rugby preparation by Bompa which follows his periodization principles (applied to rugby). I guess the best part of the book is aerobic training, although I own it but haven’t read it yet 
Anyway, the solution depends on the team level. My opinion would be to use first 4-6 weeks for complex-parallel and see how it goes. You would have strengths-weakness evaluation during this time and helps you plan the next 13 weeks better. Also, the complex-parallel will develop longer ‘residual’ effects over those 2 weeks off. Although, you can’t just jump to complex-parallel full volume, you would need a week or two of introduction (increasing volume and intensity).
You can start with:
2x full body strength training
1-2x speed work (start with hills, it is ‘easier’) and some explosive work (mb throws, hurdles jump and stick, etc)
1 glycolitic work (from week 2 or 3)
2 aerobic training sessions
Plan progression in each separatelly, don’t do too much volume and intensity from day 1…
After the two weeks off, evaluate what are the weaknesses and strengths and work on them using ‘block’ approach during the next 13 weeks.
Another approach would be to use two Accumlation periods instead of complex-parallel + block.