I think that the block with becket up top and block on your chair , and hauling from your chair, yeilds three to one, right ? it would be two to one for someone standing on deck to pull you up.
The issue of getting your line caught up on deck can be addressed like Ian suggested, or if you are really worried just keep the fall with you, which I have done in certain situations. Sure, you get heavier as you go up, but with two ratchets I find that I can stop at any point and let go of my weight and rest, with the ratchets holding me well. I have a lot of fatih in ratchets I guess, but I also never actually let go of the hauling end unless it is tied to my chair.
I only find this system to suck if you need to get right to the masthead, which I wear a climbing harness (petzl's deck ware pro harness) and use a lashing of 1/4" conception about 5' long to make a little purchace and haul myselft the rest the way up , or over or where ever I need to go.
Do hold on with your legs as you go, and take a rest if your getting tired. You dont want to faituge or hurt yourself halfway up. Granted, I don't yet know what I'll do when I am sixty
I have seen the extention ladder before and it seems to be a very dangerous and damaging practice. Also, it must me something more than a one man job to balance and raise a ladder up the rig on a sailboat without damamging anything. I will say that I have used A-frame ladders , the kind that fold flat for storage, set on deck and lashed at the feet and to the rig so made immobile, to speed up the installations of spin pole handlings systems, laying out, drilling and tapping from chair with two drills, goop and assorted fastners is slow, but a ladder cuts the time in half I find. Usefull for questus and SSB antenna work aswell.
Climb safely