Sure, you can remove the BeoLab from the base. There is some info on BeoCentral" target="_blank">https://beocentral.com/beovoxpenta">BeoCentral that suggests "all that [is] needed [is] to shorten the mounting studs and fit the stands directly to the bottom of the cabinet".

I have taken a look at the mountings studs and they are screw-threaded on either end, but not all the way along the shaft, so I'm not sure how you could shorten them.  Getting a shorter alternative would seem to be the best option. I broke one of the mounting studs on my Beolab Penta and I contacted Quality" target="_blank">https://www.quality-dream-audio.co.uk/">Quality Dream Audio to ask if they had any spare.  They did, and they sold them to me quite cheap.  It might be worth contacting them to ask if they have any Beovox Penta studs.

If you're removing the amplifiers then you don't need to use the studs at all. Just use some new bolts to bolt the base plate into the threaded holes for the studs on the base of the speaker body.