In a basis trade, if you short the Treasury futures and buy the underlying bond and hold it to maturity, is funding the only source of risk assuming there no CTD switches. You have locked in the financing rate (repo) on the bond and the futures leg doesn't require financing. Your return would be implied repo - actual repo.
Is there a way to enhance the return you earn and is this practical? For example, can you lock in the repo and receive OIS swap rate, then paying rolling overnight Fed funds rate. The cash flow you're left with is
implied repo - actual repo + (OIS - rolling overnight Fed Funds)
If rolling overnight Fed Funds = OIS rate that you locked in, then your return is just implied repo - actual repo + 0
However, if rolling overnight Fed funds < OIS rate, then your return would be higher: implied repo - actual repo + (OIS > rolling overnight Fed Funds).