Adding the 2" standpipe may be the best you can do.
About fifty years ago in the States, washers were run with 1-1/2" lines. It was kind of iffy though.
Adding the 2" standpipe helps a bit though.
Anytime you are installing a new line, of course using 2" all the way is better. In some places here, they now require a 3" line after the p-trap for suds control.
I've seen cases where a 3" line in a crawlspace that wasn't graded properly caused soap suds to come out under a toilet.