What a pretty thing! I'd be inclined to take big loppers and just cut off right at ground level any of the branches/trunks that are near, or heading out towards the walkway. That would include cutting off all the new suckers that are on the sides near the walkway. This way, instead of encouraging a bushy congested form for next year, (which you'll have if you chainsaw it) you're encouraging it to put up new growth on the side away from where you walk. Eventually, the whole bush will be a little further away from the sidewalk if you keep doing this. The stems that do bend out towards the sidewalk could be restrained with 3 stakes and a string so they stand up straight enough for you to pass. You could also prune out the oldest stems after it loses its leaves in the fall, to keep it thinned out.
The rule of thumb that I live by is to never cut away more than 1/3 of the green growth at any one pruning. The plant will surely be set back if you whack it down to 18in. in the middle of summer.
Every time I've set my spousal unit loose with a power tool in the garden, he just can't stop and the whole plants disappear . . .
He never steps back for a look when he's part way through. Now, I do the chainsawing myself, and he just sets me a 'rule' that he shall be able to walk around the house without any plants touching him. I'll tellya, in Florida that's a constant challenge.
