any providers known to be open to things like meeting at a mall and going to car in garage for a romp or bj? also possibly places like Blue Hills in certain spots, changing rooms in dept stores, restaurant or bar rest rooms, college or public library, a beach during the day between some dunes, Yawkey Way before a sox game (kidding)? risky behavior no doubt but an added rush I think. Soon too cold for a few but maybe slope side off a ski trail? I know of one provider who actually suggested Blue Hills but said rattle snakes there too...kind of a buzz kill if you spot one.
...I'm always trying to lure gentlemen onto my balcony for some naughty behavior when my hotel room has one. I also love playing in unconventional places! The risk/thrill really turns me on! I won't treat those kinds of adventures as Outcalls, for sure though. That kind of fantasy fulfillment requires multi-hour bookings so we can travel to our location together and aren't pressed for time... And of course, safe sane and consensual, always.
Many of the places you suggest, even changing rooms(!), have TV cameras in them. These cameras are becoming ubiquitous owing to their low cost and the ability for them to get on the internet so easily.
The biggest problem might not even be the authorities coming to get you, but that you could end up being on You Tube, or even You Porn, without you being aware of it.
I don't believe, I could be wrong, security cameras are allowed to monitor inside the actual dressing room. Couple of variables 1) definitely is oral only 2) gentleman has to be quick about it. A female trying on lingerie is the best scenerio for a male companion to be allowed to join but, it could be a hit or miss.
The above has worked for me. Of course, if Mr. Fisher correct, I may never try on anything except at home!
Bucket seats are advantageous for car adventures.
Yep, it's known or rumored, you could come across a rattlesnake in Blue Hills if you venture off the trail. Just reconfirmed that with someone I ran into at Starbucks.
Crowded beaches are difficult, they're pretty deserted now though.
Laughing at the idea of Yawkley Way 
I, personally, don't want to be in porn unless I'm getting paid!
The biggest problem might not even be the authorities coming to get you, but that you could end up being on You Tube, or even You Porn, without you being aware of it.
Fucking in the Blue Hills is great. I have hit a bunch of spots there and have had some incredibly great times. Keep in mind you are not alone. Big gay pick up area. Plenty of other folks looking for that spot just far enough from the road to be out of sight but not looking for a hike. Once I was there with my girlfriend and she's in her heels and I'm in my dress shoes. Sure, we're going hiking! And then you get all those mosquito bites on your butt. Try explaining that to your spouse!
There used to be a great dead end on the Canton side of the Rte 128/University Ave station, but since I was a frequent flier there they have added more patrols and god-awful street lighting. End of story.
And then there is just about every single garage in Boston. May not be convenient for screwing, but a BJs and a little pussy licking are always fun in those spots, IMHO.
Words to live by: "Hooray, hooray, the First of May; outdoor fucking starts today."
Have fun!