It is almost impossible to rebuild a wheel (i.e., new hub and new spokes) without removing the tire. Leaving the tire on, would mean leaving the spoke nipples in place. (It is a good idea to replace the spoke nipples when rebuilding a wheel. You will also require new spokes). It is a big hassle threading the spoke into nipples that are stuck in one position. Almost all wheel builders will first remove the tire. It should be possible to carefully remove and reuse your tubular tire anyway, so this may be less of an issue than you think. (What adhesive did you use?)
11-speed compatibility options
In terms of replacing your hub to get 11 speed compatibility. There are a few different options to consider. Custom wheel builds are not cheap. If your rims are not in pristine condition or insanely expensive it may be more cost effective to sell your wheels (or wheelset) and buy purchase a replacement wheelset that is 11 speed compatible. (Note an 11-speed rear wheel can take 10-speed cassettes with the appropriate spacer). You may also check what rear hub you have, some more recent hubs that started their life as 8/9/10 speed hubs were designed to allow the cassette freehub bodies to be changed in order to enable 11-speed compatibility (although this is not a common feature, it does exist and you may be lucky enough to own one).