What size manifold for 1" pipe from meter?
If you're going to re-build all the piping only for this pressure issue I suggest you to first try adding a flow reducers to toilets, washing machines and to all those supplies where a reduced flow is still acceptable. In this case pressure unbalancing will be reduced without affecting comfort or efficiency.  

Anyway I suggest you to keep the cold piping as big as you can (1" is good) for the main conduit (where it splits to water heater and to each bathroom and kitchen lines where you can start with 3/4) as it will greately reduce pressure unbalances. If you use PEX, check pipe is PEX-c using lower grades (a or b) will be penny-savy pound-foolish. Pex c mean it's phisically-reticolated, pex-b is temperature-reticolated (but sometimes the last 'hot bath' is never done leading to premature failures) and pex-a is chemically-reticolated won't be guaranteed to last 50 years but it's not as bad as pex-b. 

There are also 'unreticolated' pipes, those should be absolutely avoided as may break with hot water or high pressures so look for *PE-Xc/Al/PE-Xc * printed on pipe.