No, it wouldn't be an issue. You can exit straight away. I guess you're looking to take the ICE to Cologne, the connection is easy but it can be stressful -> follow this advice : https://www.seat61.com/stations/brussels-midi.htm#Short_cut
EDIT : since your train is continuing to the Netherlands the ICE might be waiting on the same platform !
One other tip: don’t ask Eurostar staff, just get off.
If you ask, it’s possible they will invent some reason why you can’t do it!
Will you take the IC(E) or the sleeper train to get to Berlin?
If ICE, before you get out, check if your ICE will effectively be leaving from Brussels on www.bahn.com or https://www.b-europe.com/EN/. Cancellations and delays are very frequent on these train set (they’re plagued by technical issues).
If cancelled, you’re better of continuing to Amsterdam, to directly get on the IC to Berlin.
Cheers, I'll bear that in mind.
I'd get off at Brussels head to Koln then up
Perhaps unsurprisingly the connection at Brussels was cancelled. I got the next ICE to Cologne which worked relatively well until they decanted everyone at Cologne due to technical issues. Caught the last connection to Berlin but everything slowed down after Hanover and arrived in Berlin 45 mins late. Seems German trains aren't what they were...
Yeah trains are really good (except the infamous ICE3M which is due to be replaced soon) but the infrastructure is in a bad state due to a lack of maintenance in the last decades, it’s a fact. Fortunately there are long-term investments taking place : all major mainlines will be completely rebuilt in the coming years. Starting with the Riedbahn (Frankfurt - Mannheim) from July to December of this year.
All in all it’ll mean a few extra years of chaos but it should improve gradually!
Got 2 x 15 Day passes in Nov Sale so I'll be heading this way twice soon!
Did Sweden & Norway in Sept , it was a nightmare , First Day Malmö to Gothenburg all got thrown off the train with 300 km to go Points Failure , train was full left to our own to make our own way. Took 2 months to get compensation back .Bridges washed away in Norway , lots of Bus replacements , European Rail networks are creaking