if you're going to pull the engine anyway and if it has at least 100k mi, maybe do the head gaskets too for good measure. certainly if you have 150k mi and they haven't been done before. it would be bad to be enjoying your new clutch and soon after have to pull the motor again.
BTW do you or others know if there is an improved Subaru or aftermarket clutch design? I owned 2 different '00s and the clutch shudder was bad at times. It was unpredictable and always did it from the time I got them at about 85 to 100k mi. I didn't keep them long enough to really figure that out, though. (First one wife totaled, second traded for '04).
I would just take my time and do it right.. Pull the engine.. Its not hard to find a engine hoist to rent..
Also while its out check with Subaru to see if there are any upgrades.. Seems to me they did an upgrade to the piece that holds the rear main seal in or some thing like that.. And you might as well replace rear seal any way..
As far as the head gaskets.. Not much of a job with it setting on the bench.. I would just do it..
Also think about doing the water pump, Thermostat, Front oil seal, timing belt tensioner and any thing else you question, and of course the timing belt while its out.. No much of a job with it on the bench.
Its not uncommon to see Foresters that are taken care of with 350,000 miles on them..
the upgrade you're probably thinking about is newer models have a metal "oil separator plate" on the rear of the motor between the 2 "halves" instead of a plastic one that tends to crack and leak with age. it is a no-brainer to do that too.