I've been doing a little research on the same subject. I know that Stihl, Echo, and Poulan have a number of different multi-tool systems available. Just do a search as follows and it should take you to see what's available:
"Echo Pro Attachment Series"
"Stihl Multi-task tools"
"Poulan Pro attachments"
I imagine there are more brands available.

Its early yet, I do nothing about leaves. Very few are left come first mow in the spring. :)

Multi tool systems are a fantastic concept. I've looked into them a little, but always stopped when I got into the $$ for a "name brand," e.g. Stihl.

I guess the advantage would be only one two cycle engine to keep happy, the disadvantage would be if that engine gets cranky.....:-(

I was looking for a leaf blower/vac a while back and was also thinking of replacing the weed eater (Stihl). After looking around, ended up spending a few bucks on the weedeater and purchased a blower/vac (reconditioned full warranty) from Amazon for something like $70 deivered. That was 4 years ago, the reconditioned machine runs great, both my brother and I use it and no problems.

Guess there's also the question of how much you'll use the device? Two cycle engines like to be run, and are not as happy sitting idle. Multi tool machine you'd use all spring, summer and fall, where a leaf blower would have limited use and sit idle. Small tillers/cultivators are used in the spring and then sit idle.

I've decided to stay with "pupose built" tools as opposed to "one size fits all."

Good luck,

Ev