some interesting advise here, im not going to try and tackle all the different points, just throw in my two cents
heres what worked pretty well for me
assuming no major injuries (which is a pretty massive assumption in rugby) and starting at the end of the previous season i would take a 1-2 week rest depending how trashed my body felt
then i had a 6-10 week pure strength phase (depending on whether i was press-ganged into playing 7s). i didnt do any conditioning, or much volume really, during that time, just try and get really strong (im a prop).
this would usually take me towards the end of july/beginning of august (european rugby season) which is when i would increase the volume in the weight room and start getting out for some general conditioning (sprints, agility work, etc.).
no matter what, for me, preseason is always brutal. rugby is so positionally specific and group training sessions (especially preseason break-you-down, build-you-up sorta stuff that seems to prevail with old school coaches) just aren't. i found it far more beneficial to focus on what i needed for my position in the offseason and then jump back into getting fit for the field when preseason starts. after all nothing will ever make you match fit apart from matches.
in season speed work was my best friend. i've always found speed work (think: westside dynamic effort) adequate to maintain strength (and guess what you gain speed, strength x speed = power). this worked for me for a few reasons. mostly psychologically i was too beat to contemplate getting under a really heavy bar, and the recovery just couldnt justify the "gains", which never really materialise in season anyway. equally, the light(er) weights (not lowered intensity mind) of speed work, and using full ROM movements explosively, would clear out all the junk building up locally in low back, hips, etc. and help maintain joint mobility.
anyway, bit rambly, but hey, thats what worked for me
what position do you play/for who?