Drafting a new constitution is fairly unnecessary outside of deposing an aristocracy or a dictatorship. Plus, it only has any effect if everyone agrees on it so you will need literally everyone to have some input and agree or else you will have seperationists.
I would just add the following and call it good:
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No cap on the house of Representatives.
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Term limit on EVERY elected individual, cabinet appointee, and judge.
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Senate seats proportional to population with the smallest state receiving 1, a state double its size receiving 2, etc.
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The President is not immune to indictment and has no authority over the DOJ.
EDIT:
\5. Individual campaign funds are capped, organizations funds require signatures and count towards the individual totals, with enforcement of federal prison time on ALL involved in the case of going over. Proven illegal funding can invalidate election results and trigger a new election automatically.
\6. In the event of an absence a new election must be called immediately, and any attempt to delay the process can be met for prison time.
\7. Total Bodily Autonomy - doctors are still expected to adhere to strict antinegligience practices and conditions, can choose to decline patients, but if a patient is informed of risks for proven safe procedures then it is their choice to have whatever medical procedure or even cosmetic procedure performed on their body as they wish.