There is another way to increase pressure slightly without installing a pump.
Enlarge the water tank outlet hole to 2" diameter pipe and use several reducer fittings to gradually step down to standard 1/2" before the concealed pipeline.

Install a booster pump is much easier solution, instead of reconnecting the pipe to the direct source.

Direct source pressure may be fluctuating as well, at night, pressure normally higher, which may premature result valve leaking issue, concealed pipe leaking (although this can be mitigated by pressure regulator, but installing mean extra money needs to fork out, not to mention pressure regulator does wear out over the time as well).
While for peak water usage time, like evening, pressure may drop due to many users open their tap.

Also, if direct source water pressure is too low time, you suffer low pressure as well.
While if install booster pump, you have no such an issue

So more cost effective and simple way is to install booster pump.

Summarise, 2 way to increase pressure

a) install booster pump, just minor work needed.

b) reconnecting to direct source that need to redesign/reconnect piping + pressure regulator, no guarantee to have good pressure if direct source pressure is poor.