Yes, it can be changed, but that would require rewrites of almost all templates, making style incompatible with almost all plugins and making it harder to upgrade. Its fun to do for test, but its a bad idea for release.

vBulletin is not completely customisable. Its quite far from it. Templates are being included in eachother without any connection between them (so there is absolutely no control over loops), so, for example, if you have a forumhome_forumbit_level1_nopost template and inside it in $childforumbits, you don't know how many subforums are in it, you don't know if that level1 forum was first, last or somewhere in middle. Templates can't be included by designer. There are spacer_open and spacer_colse templates that are required in many places and impossible to get rid of.

Also for some reason threaded and hybrid views don't work with tableless layout, I have no idea why it happens, but it did happen when I was testing it (all named divs were there and in all parent templates).