I have bought a T1500 frame, but have not opted to buy their handlebars.
If it is possible to route the Speeder handlebars with a 105 hydraulic disc groupset on the T1500 frame then I might compromise. However, if this is potentially going to lead to problems, then I need to find something else.
Any particular reason you opted not to buy the Winspace handlebars? That would have inherently resolved the cable routing issue, since the handlebars have additional ports/outlets underneath to accommodate externally routing the mechanical shift cables into each side of the frame downtube.
Assuming Winspace has your handlebar size in stock and you're comfortable with the drop, reach, and -10 stem angle...I cannot recommend their handlebars enough. Looking at those Speeder handlebars, the outlets/ports near the drops do not look wide enough to fit both a hydro and mechanical shift cable. Probably intended for Di2 or eTap.
Alternatively you can run a separate handlebar stem combo using either FSA's ACR or SRS no. 69 system.