New Tape Needed
General wisdom on tubulars is that the base tape NEEDS to be a single contiguous piece with one overlapping joint. This helps stablize the tire when fully inflated.
If you decide to go for the repair route, I would say that you need to overlap the new basetape about one inch on both ends of the repair. This might result in a noticable hop or bulge when the tire is remounted.
The safest bet is to replace the entire base tape. You can go ahead and send it out, or do it yourself. The home repair has the likelyhood of not being uniform and the end result being an unstable tire once mounted again.
Personally, I would do the patch repair and religate the tire to the spares pool. YMMV