It kinda depends on your group. My group let someone treat a leman russ as a baneblade because we got together about 15 guys with 1000-2000 point armys to do some
apoc, and one of the 4 guys who actually had a super heavy found out that his glue was rubbish and his recently-bought baneblade fell apart

. But my group is pretty lax and that was very situational. I know that I would be fine with it, but you might wanna just glue a weird gun on him and a couple pipes+stikkbombs and count it as mek's tools

.